ASTM D6421-20

Standard Test Method for Evaluating Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling by Bench Procedure

SIGNIFICANCE AND USE
5.1 Driveability problems in PFI automobiles were first reported in 1984. Deposits are prone to form on the metering surfaces of pintle-type electronic fuel injectors. These deposits reduce fuel flow through the metering orifices. Reductions in metered fuel flow result in an upset in the air-fuel ratio, which can affect emissions and driveability. When heavy enough, these deposits can lead to driveability symptoms, such as hesitation, hard starting, or loss of power, or a combination thereof, that are easily noticed by the average driver and that lead to customer complaints. The mechanism of the formation of deposits is not completely understood. It is believed to be influenced by many factors, including driving cycle, engine and injector design, and composition of the fuel. The procedure in this test method has been found to build deposits in PFIs on a consistent basis. This procedure can be used to evaluate differences in base fuels and fuel additives. A study of PFI fouling was conducted in both the bench test and the vehicle test procedures to obtain a correlation. The vehicle tests were conducted as described in Test Method D5598. The tests were conducted on several base gasolines, with and without additives blended into these base fuels. The PFI bench test proved to be reliable, repeatable, and a good predictor of PFI fouling in test vehicles.  
5.1.1 State and Federal Legislative and Regulatory Action—Legislative and regulatory activity, primarily by the state of California (see 2.3) and the federal government (see 2.4), necessitate the acceptance of a standard test method to evaluate the PFI deposit-forming tendency of an automotive spark-ignition engine fuel.  
5.1.2 Relevance of Results—The operating conditions and design of the laboratory apparatus used in this test method may not be representative of a current vehicle fuel system. These factors must be considered when interpreting results.  
5.2 Test Validity:  
5.2.1 Procedural Compliance—The test ...
SCOPE
1.1 This test method covers a bench test procedure to evaluate the tendency of automotive spark-ignition engine fuel to foul electronic port fuel injectors (PFI). The test method utilizes a bench apparatus equipped with Bosch injectors specified for use in a 1985-1987 Chrysler 2.2 L turbocharged engine. This test method is based on a test procedure developed by the Coordinating Research Council (CRC) for prediction of the tendency of spark-ignition engine fuel to form deposits in the small metering clearances of injectors in a port fuel injection engine (see CRC Report No. 592).2  
1.2 The test method is applicable to spark-ignition engine fuels, which may contain antioxidants, corrosion inhibitors, metal deactivators, dyes, deposit control additives, demulsifiers, or oxygenates, or a combination thereof.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  Specific precautionary statements are given throughout this test method.
Note 1: If there is any doubt as to the latest edition of Test Method D6421, contact ASTM International Headquarters. Other properties of significance to spark-ignition engine fuel are described in Specification D4814.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Mar-2020
• ICS: 27.060.10 - Liquid and solid fuel burners
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.A0.01 - Gasoline and Gasoline-Oxygenate Blends

Relations

• Replaces: ASTM D6421-19 - Standard Test Method for Evaluating Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling by Bench Procedure
• Effective Date: 01-Apr-2020
• Refers: ASTM D4814-24 - Standard Specification for Automotive Spark-Ignition Engine Fuel
• Effective Date: 01-Jan-2024
• Refers: ASTM D4175-23a - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 15-Dec-2023
• Refers: ASTM D4814-23a - Standard Specification for Automotive Spark-Ignition Engine Fuel
• Effective Date: 01-Dec-2023
• Refers: ASTM D4175-23e1 - Standard Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Jul-2023
• Refers: ASTM D5500-20a - Standard Test Method for Vehicle Evaluation of Unleaded Automotive Spark-Ignition Engine Fuel for Intake Valve Deposit Formation
• Effective Date: 01-Jun-2020
• Refers: ASTM D5598-20 - Standard Test Method for Evaluating Unleaded Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling
• Effective Date: 01-Apr-2020
• Refers: ASTM D4814-20 - Standard Specification for Automotive Spark-Ignition Engine Fuel
• Effective Date: 01-Feb-2020
• Refers: ASTM D4814-19a - Standard Specification for Automotive Spark-Ignition Engine Fuel
• Effective Date: 01-Dec-2019
• Refers: ASTM D5598-19 - Standard Test Method for Evaluating Unleaded Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling
• Effective Date: 01-Nov-2019
• Refers: ASTM D5500-19 - Standard Test Method for Vehicle Evaluation of Unleaded Automotive Spark-Ignition Engine Fuel for Intake Valve Deposit Formation
• Effective Date: 01-Nov-2019
• Refers: ASTM D5500-18 - Standard Test Method for Vehicle Evaluation of Unleaded Automotive Spark-Ignition Engine Fuel for Intake Valve Deposit Formation
• Effective Date: 01-Dec-2018
• Refers: ASTM D5598-18 - Standard Test Method for Evaluating Unleaded Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling
• Effective Date: 01-Dec-2018
• Refers: ASTM D4814-18c - Standard Specification for Automotive Spark-Ignition Engine Fuel
• Effective Date: 01-Oct-2018
• Refers: ASTM D4814-18a - Standard Specification for Automotive Spark-Ignition Engine Fuel
• Effective Date: 01-Apr-2018

Overview

ASTM D6421-20 is a standard test method developed by ASTM International for evaluating the tendency of automotive spark-ignition engine fuel to foul electronic port fuel injectors (PFI) using a bench procedure. PFI fouling can significantly impact vehicle driveability and emissions by altering the air-fuel ratio, leading to problems such as hesitation, hard starting, and loss of power. This standard outlines a laboratory bench test that replicates deposit formation on fuel injectors, allowing stakeholders to assess differences in fuels and additives for controlling such deposits.

Key Topics

• Port Fuel Injector Fouling: Describes the tendency of fuel injectors to accumulate deposits, which can reduce fuel flow and negatively affect engine performance and emissions.
• Test Methodology: Outlines a consistent, repeatable bench procedure employing Bosch injectors from specified turbcharged engines. The process simulates fuel system conditions to rapidly build deposits on injectors.
• Fuel and Additive Evaluation: The method can be used to compare base fuels and deposit control additives for their effectiveness in reducing injector fouling.
• Regulatory Relevance: The test methodology was developed in response to regulatory and legislative activities (notably in California and under the U.S. Clean Air Act) requiring a standardized process for evaluating PFI deposit-forming tendencies.
• Interpretation Cautions: The laboratory apparatus and test conditions may not exactly replicate modern vehicle systems. Users should be cautious in extrapolating results to real-world vehicle operation.

Applications

ASTM D6421-20 offers practical solutions for several stakeholders in the automotive and fuel industries:

• Fuel Manufacturers: Enables evaluation of spark-ignition engine fuels-including those containing additives such as antioxidants, corrosion inhibitors, metal deactivators, and deposit control agents-for PFI deposit-forming tendency.
• Additive Suppliers: Provides a reliable procedure for demonstrating the effectiveness of deposit control additives in preventing or minimizing injector fouling.
• Engine and Vehicle Manufacturers: Assists in assessing whether specified fuels are likely to cause injector-related driveability or emission issues in port-fuel-injected engines.
• Regulatory Compliance: Supports compliance efforts by providing an accepted, standardized method recognized in both state and federal regulatory frameworks.
• Research and Development: Facilitates scientific studies on the interactions between fuel composition, additive technology, engine design, and real-world driveability outcomes.

Related Standards

Users of ASTM D6421-20 may also reference these related documents for additional context or complementary procedures:

• ASTM D4814: Specification for Automotive Spark-Ignition Engine Fuel
• ASTM D5598: Test Method for Evaluating Unleaded Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling (vehicle test)
• ASTM D5500: Test Method for Vehicle Evaluation of Unleaded Automotive Spark-Ignition Engine Fuel for Intake Valve Deposit Formation
• ASTM D4175: Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
• CARB PFI Test Methods: California Air Resources Board’s procedures for evaluating injector deposits
• ANSI MC 96.1: American National Standard for Temperature Measurement Thermocouples

Practical Value

ASTM D6421-20 delivers a repeatable, predictive, and bench-scale approach to assessing injector fouling, bridging the gap between laboratory screening and vehicle testing. The standard is integral for quality control, fuel development, emission compliance, and ensuring consumer satisfaction by reducing vehicle performance issues linked to fuel injector deposits.

Keywords: ASTM D6421-20, spark-ignition engine fuel, port fuel injector (PFI) fouling, bench test procedure, fuel additives, automotive fuel standards, deposit control additive, driveability, emissions, fuel quality testing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6421 − 20
Standard Test Method for
Evaluating Automotive Spark-Ignition Engine Fuel for
Electronic Port Fuel Injector Fouling by Bench Procedure
This standard is issued under the fixed designation D6421; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
1.1 This test method covers a bench test procedure to
Barriers to Trade (TBT) Committee.
evaluate the tendency of automotive spark-ignition engine fuel
to foul electronic port fuel injectors (PFI). The test method
2. Referenced Documents
utilizes a bench apparatus equipped with Bosch injectors
2.1 ASTM Standards:
specified for use in a 1985-1987 Chrysler 2.2L turbocharged
D4175Terminology Relating to Petroleum Products, Liquid
engine.Thistestmethodisbasedonatestproceduredeveloped
Fuels, and Lubricants
by the Coordinating Research Council (CRC) for prediction of
D4814Specification for Automotive Spark-Ignition Engine
the tendency of spark-ignition engine fuel to form deposits in
Fuel
the small metering clearances of injectors in a port fuel
2 D5500Test Method for Vehicle Evaluation of Unleaded
injection engine (see CRC Report No. 592).
Automotive Spark-Ignition Engine Fuel for Intake Valve
1.2 The test method is applicable to spark-ignition engine
Deposit Formation
fuels, which may contain antioxidants, corrosion inhibitors,
D5598Test Method for Evaluating Unleaded Automotive
metal deactivators, dyes, deposit control additives,
Spark-IgnitionEngineFuelforElectronicPortFuelInjec-
demulsifiers, or oxygenates, or a combination thereof.
tor Fouling
1.3 The values stated in SI units are to be regarded as 2.2 ANSI Standard:
standard. The values given in parentheses after SI units are MC96.1AmericanNationalStandardforTemperatureMea-
providedforinformationonlyandarenotconsideredstandard. surement Thermocouples
2.3 CARB Standard:
1.4 This standard does not purport to address all of the
Test Method for Evaluating Port Fuel Injector (PFI) Depos-
safety concerns, if any, associated with its use. It is the
its in Vehicle Engines
responsibility of the user of this standard to establish appro-
2.4 Clean Air Act Amendment:
priate safety, health, and environmental practices and deter-
Clean Air Act Amendments of 1990, Public Law 101–549,
mine the applicability of regulatory limitations prior to use.
Title 1 –Provisions for Attainment and Maintenance of
Specificprecautionarystatementsaregiventhroughoutthistest
National Air Quality Standards
method.
NOTE 1—If there is any doubt as to the latest edition of Test Method 3. Terminology
D6421, contact ASTM International Headquarters. Other properties of
3.1 For general terminology, refer to Terminology D4175.
significance to spark-ignition engine fuel are described in Specification
D4814.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
This test method is under the jurisdiction of ASTM Committee D02 on Standards volume information, refer to the standard’s Document Summary page on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of the ASTM website.
Subcommittee D02.A0.01 on Gasoline and Gasoline-Oxygenate Blends. Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
Current edition approved April 1, 2020. Published April 2020. Originally 4th Floor, New York, NY 10036, http://www.ansi.org.
approved in 1999. Last previous edition approved in 2019 as D6421–19. DOI: Available from California Air Resources Board, P.O. Box 2815, Sacramento,
10.1520/D6421-20. CA95815. (Incorporated by reference in California Code of Regulations, Title 13,
“AProgram to Evaluate a Bench Scale Test Method to Determine the Deposit Section 2257.)
Forming Tendencies of Port Fuel Injectors,” available from Coordinating Research AvailablefromU.S.GovernmentPrintingOfficeSuperintendentofDocuments,
Council, Inc., 5755 North Point Parkway, Suite 265, Alpharetta, GA 30022, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
http://www.crcao.org. www.access.gpo.gov.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6421 − 20
3.2 Definitions: an aluminum block.Astainless-steel internal reservoir is filled
3.2.1 base fuel, n—in automotive spark-ignition engine with 2L of the test fuel.
fuels,amaterialcomposedprimarilyofhydrocarbonsthatmay
4.4 During one 60min test cycle, the fuel injectors are
also contain oxygenates, anti-oxidants, corrosion inhibitors,
pulsed for 15s, followed by a 50min hot-soak interval in
metal deactivators, and dyes but does not contain deposit
whichtheinjectoraluminumblocktemperaturecontrollerisset
control or lead additives. D5500
at a temperature of 160°C (320°F) and the fuel pressure is
regulated to 263 kPa(38psig), followed by a 10min cool-
3.2.1.1 Discussion—A jurisdiction may set limits on lead
down period. Flow measurements for each of the injectors are
content from all sources.
takenatthebeginningofthetest,after22cycles,andattheend
3.2.2 deposit control additive, n—material added to the fuel
of the test at 44 cycles.
topreventorremovedepositsinoneormoreoftheenginefuel,
intake, and combustion systems. D5500 4.5 Thechangeintherateofflowforeachinjectorfromthe
3.2.2.1 Discussion—For the purposes of this test method, start to the end of the test is used to determine the fouling
the performance of a deposit control additive is limited to the percentage of each injector.
electronic port fuel injector tip areas.
5. Significance and Use
3.2.3 driveability, n—in vehicles equipped with internal
5.1 Driveability problems in PFI automobiles were first
combustion engines, the quality of a vehicle’s performance
reported in 1984. Deposits are prone to form on the metering
characteristics under a range of conditions as perceived by the
surfaces of pintle-type electronic fuel injectors.These deposits
operator. D4814
reduce fuel flow through the metering orifices. Reductions in
3.2.3.1 Discussion—The operating conditions may include
metered fuel flow result in an upset in the air-fuel ratio, which
cold starting and warm-up, acceleration, idling, and hot start.
can affect emissions and driveability. When heavy enough,
Theperformancecharacteristicsmayincludeenginehesitation,
these deposits can lead to driveability symptoms, such as
stumble, and stall. D4814
hesitation, hard starting, or loss of power, or a combination
3.3 Definitions of Terms Specific to This Standard:
thereof, that are easily noticed by the average driver and that
3.3.1 cycle, n—a 15s pulsing period, followed by a 50min
lead to customer complaints. The mechanism of the formation
heating period at 160°C (320°F), followed by a 10min
of deposits is not completely understood. It is believed to be
cool-down period.
influenced by many factors, including driving cycle, engine
andinjectordesign,andcompositionofthefuel.Theprocedure
3.3.2 electronic port fuel injector (PFI), n—an electrome-
in this test method has been found to build deposits in PFIs on
chanical device used to control fuel flow in an internal
a consistent basis. This procedure can be used to evaluate
combustion engine.
differences in base fuels and fuel additives. A study of PFI
3.3.3 fouling, v—formation of carbonaceous deposits on the
fouling was conducted in both the bench test and the vehicle
pintleormeteringsurfacesofanelectronicfuelinjector,which
test procedures to obtain a correlation. The vehicle tests were
reduces fuel flow rate.
conducted as described in Test Method D5598. The tests were
3.3.4 pintle, n—a needle-like metering device extending
conducted on several base gasolines, with and without addi-
beyond the electronic fuel injector body that is part of an
tives blended into these base fuels. The PFI bench test proved
electronic fuel injector, which controls flow rate and spray
to be reliable, repeatable, and a good predictor of PFI fouling
pattern.
in test vehicles.
5.1.1 State and Federal Legislative and Regulatory
3.3.5 test fuel, n—base fuel, with or without the addition of
Action—Legislative and regulatory activity, primarily by the
a deposit control additive, that is used for evaluation as
state of California (see 2.3) and the federal government (see
described in this test method.
2.4), necessitate the acceptance of a standard test method to
evaluate the PFI deposit-forming tendency of an automotive
4. Summary of Test Method
spark-ignition engine fuel.
4.1 This test method describes a procedure for evaluating
5.1.2 Relevance of Results—The operating conditions and
the formation of deposits in PFIs. The test method includes a
designofthelaboratoryapparatususedinthistestmethodmay
bench test procedure that has been shown to rapidly form
not be representative of a current vehicle fuel system. These
deposits in fuel injectors and a procedure for determining
factors must be considered when interpreting results.
resultant flow loss.
5.2 Test Validity:
4.2 Thistestmethodusesasimulatedfuelsystemconsisting
5.2.1 Procedural Compliance—The test results are not con-
of a fuel pump, filter, pressure regulator, fuel rail, and fuel
sideredvalidunlessthetestiscompletedincompliancewithall
injectors. A heat source is applied to the fuel injectors to
requirements of this test method. Deviations from the param-
simulate the hot-soak portion of the vehicle test (see Test
eterlimitspresentedinSection10willresultinaninvalidtest.
Method D5598).
Engineering judgment shall be applied during conduct of the
4.3 Each test begins with screened injectors that are known testmethodwhenassessinganyanomaliestoensurevalidityof
to foul.The tips of these four clean fuel injectors are placed in the test results.
D6421 − 20
6. Apparatus 6.3.2 Graduated Cylinders—Four graduated cylinders of
50mLor100mLcapacity,accuratetothenearestmillilitreare
7,8
6.1 Automatic Electronic PFI Bench Test Apparatus —
recommended for use in flow testing.
This apparatus is composed of two units, a fuel handling unit
6.3.3 Low Voltage Power Supply—A 12V, variable, direct
and a controller.
current power source should be used in cleaning of the
6.1.1 Fuel Handling Unit—This unit houses a machined
injectors.
aluminum fuel rail and a heated aluminum block designed to
6.3.4 Ultrasonic Bath—An ultrasonic bath with heating
accommodate four PFIs. Heaters and thermocouples are
capabilities should be used for the cleaning of the injectors.
mounted in the heated aluminum block. This unit also houses
6.3.5 Pipette Bulb—A pipette bulb should be used to draw
a 2.25L stainless steel reservoir, an electric fuel pump, a fuel
injector cleaning solution into the injector for cleaning.
regulator, and a variety of valves used to transfer fuel to and
6.3.6 Pipette—A disposable transfer pipette should be used
from the reservoir and to deliver fuel under pressure to the
to fill injectors with the cleaning solution during the cleaning
injectors (see Annex A1).
procedure.
6.1.2 Programmable Microprocessor Controller or Other
6.3.7 Plastic Disposable Beakers—Disposable plastic bea-
Controller—The controller is used to fill the fuel reservoir,
kersofapproximately150mLorothercontainersofequivalent
controlandmeasurethetemperatureoftheheatedblock,pulse
sizeshouldbeusedtocontaintheinjectorcleaningfluidduring
the injectors, control the soak period, count the number of test
the clean up of the injectors.
cycles, and control the flow period for the measuring of the
6.4 Data Acquisition—Adata acquisition device, capable of
flow rate. The unit is programmed to shut down automatically
collecting the raw data in accordance with 10.4, shall be
at the end of each 22-cycle period.
required.
6.1.3 External Pressure Regulator—This regulator is used
to adjust the pressure of the nitrogen gas on the fuel system.
7. Reagents and Materials
This ensures that the pressure of the fuel in the fuel rail is
7.1 Purity of Reagents—Reagent grade chemicals shall be
maintainedwithanaccuracyof 66.8kPa(61.0psi)duringthe
used for all test procedures. Unless otherwise noted, it is
test.
intended that all reagents conform to the specifications of the
6.1.4 Electronic PFIs—Only Bosch EV1.1A (Part Number
Committee onAnalytical Reagents of theAmerican Chemical
8,9
0280150360) pintle-style injectors shall be used. The corre-
Society,wheresuchspecificationsareavailable. Othergrades
spondingChryslerCorp.partnumberis4306024andisclearly
may be used provided it is first ascertained that the reagent is
marked on the injector. The protective cap shall be removed
of sufficient purity to permit its use without lessening the
from the injector by cutting the plastic cap with a razor blade
accuracy of the determinations.
and gently heating with a heat gun. The rubber o-rings and
8,
7.2 Berryman Chem-Dip Carburetor and Parts Cleaner
spacers shall be removed to expose the bare metal injector tip.
—This cleaner has been found effective in removing the
Each injector shall be screened for fouling capability prior to
deposits built up in the injectors. This cleaner or any other
use in the procedure. The screening procedure is found in
carburetor or engine parts cleaner that is proven effective in
Annex A2.
removing such deposits shall be used to clean the injectors.
6.2 Testing Area—The ambient atmosphere of the testing
(Warning—Berryman Chem-Dip contains methylene
areashallbereasonablyfreeofcontaminants.Thetemperature
chloride, monochlorotoluene, xylene, ethyl phenols, and xyle-
shouldbemaintainedat24°C 65°C(75°F 69°F).Uniform
nolsthatareextremelydangerousifinhaled,areskinirritanton
temperature is necessary to ensure repeatable injector flow
contact, and are carcinogenic.)
measurements. The specific humidity shall be maintained at a
7.3 RinsingSolvent—A1:1mixtureofisooctaneandxylene,
uniform comfortable level. (Warning—Provide adequate ven-
orsuitablemixtureofsolvents,shallbeusedtorinsethebench
tilationandfireprotectioninareaswhereflammableorvolatile
test apparatus reservoir, injectors, and fuel lines between tests.
liquids and solvents, or both, are used. Suitable protective
Approximately 1L is used.
clothing is recommended.)
7.4 Test Fuel—A test fuel is either a base fuel or a
6.3 Laboratory Equipment:
homogeneous blend of additives and base fuel.Asingle batch
6.3.1 Analytical Balance—An analytical balance capable of
shallbeblendedbeforethestartofthetest.Approximately8L
0.01g resolution with a maximum capacity of at least 200g is
(2gal) of fuel is needed for a single test.
recommended. The balance should be calibrated following the
7.5 Additive/Base Fuel—Some test requestors may require
manufacturer’s procedure and frequency recommendations.
thatthetestfuelbeblendedatthetestlaboratoryand,therefore,
7 10
The following instrument has been found suitable by interlaboratory coopera- ACS Reagent Chemicals, Specifications and Procedures for Reagents and
tive testing: Port Fuel Injector Bench Test Apparatus. Available from Southwest Standard-Grade Reference Materials, American Chemical Society, Washington,
Research Institute, San Antonio, TX. DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
If you are aware of alternative suppliers, please provide this information to Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
ASTM International Headquarters. Your comments will receive careful consider- U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
ation at a meeting of the responsible technical committee, which you may attend. copeial Convention, Inc. (USPC), Rockville, MD.
9 11
The sole source of supply of the pintle-style injectors known to the committee The sole source of supply of the cleaner known to the committee at this time
at this time is Robert Bosch Corp., 25th Ave., Broadview, IL 60153. is Berryman Co., Dallas, TX.
D6421 − 20
willsupplythedepositcontroladditiveandmay,attheiroption 9.3.1 Prior to making the measurement, bleed off any gases
or if a suitable base fuel is not available at the test laboratory, in the fuel rail (see A3.6) and discard the fuel.
supply untreated base fuel. The test requestor shall supply the
9.3.2 Measure the flow masses for the four injectors inde-
deposit control additive and, if supplied, the base fuel in
pendently.Holdtheinjectorpintleopenfor12swhilesubject-
appropriatevolumesandpackagingtoensuresafeandefficient
ing fuel to an initial nitrogen pressure of 263kPa (see 6.1.3).
handling. Blending instructions detailing the concentration
9.3.3 Recordandaveragethreeseparateflowmassmeasure-
ratio either volumetric-based or mass-based shall accompany
ments for each injector.
all deposit control additives. Mass-based measurement is
9.4 Begin test.
preferred. The blended fuel shall be clearly identified.
7.5.1 Additive/Base Fuel Shipment and Storage—The addi- 9.5 After completing 22 cycles, allow the base (aluminum
tive shall be shipped in a container as dictated by safety and block)temperaturetocoolto24°C 63°C(75°F 65°F).The
environmental regulations. The additive shall be stored in flow measurement (see A3.6) shall be performed within 4h of
accordance with all applicable safety and environmental regu- completing 22 cycles and with the same test fuel used for the
lations. pretest flow. Record flow measurement results (see A3.6) and
7.5.2 Base Fuel—The base fuel used for this test method the base temperature at which the flow measurements were
should be typical of commercial, automotive spark-ignition
generated.
engine fuel. The base fuel may contain oxygenates typical of
9.6 The test may be aborted at this point if the test
those being used commercially.
parameters detailed in 10.4 have been compromised, or if any
7.6 Nitrogen Gas (≥99.9 % Pure)—Thisgasshallbeusedto
equipmentmalfunctionhasbeendetected.Otherwise,continue
pressurize the fuel system and the fuel rail.
testing for an additional 22 cycles.
9.7 After 44 cycles have been completed, allow the base
8. Preparation of Apparatus
temperature to cool to 24°C 6 3°C (75°F 6 5°F). Perform
8.1 Fuel Injector Preparation:
the flow measurement within4hof test completion and with
8.1.1 The injectors shall be cleaned (see A3.2) prior to the
the same test fuel as used for the pretest flow. Record flow
running of the test. Proper cleaning is essential for running a
measurement results (see A3.6) and the base temperature at
valid test.
which the flow measurements were generated.
8.1.2 Check the injector flow (see A3.5). Injectors shall
meet the conditions of Annex A4 before beginning the test.
10. Calculation
8.2 Placetheinjectorsintothefuelhandlingunit(seeA3.3).
10.1 Number of Test Cycles—Complete 44 test cycles.
8.3 Pressurize the tank and the fuel lines with nitrogen gas.
Break the 44 cycles into two groups of 22 cycles run
consecutively, with a break in between of less than 4h.
8.4 Set test parameters as specified in Table 1. If using a
programmablecontroller,programthecontrollerinaccordance
10.2 Fuel Injector Flow Measurement—Statically flow test
with A3.4, or refer to your manufacturer’s manual.
(seeA3.6)injectorswhilestillintheapparatusfor12s 60.5s,
8.4.1 The test will run for 44 cycles with measurements
using the test fuel. To ensure that the test fuel completely fills
taken at the end of each 22-cycle segment.
the injector during flow testing, flush injectors for at least 10 s
with the test fuel prior to the start of the flow testing.
8.5 Add fuel to the internal fuel reservoir (see A3.5).
10.3 Calculation of Fuel Injector Fouling—Express the
9. Procedure
amount of fuel injector fouling as the percent difference
9.1 Mount screened and cleaned injec
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6421 − 19 D6421 − 20
Standard Test Method for
Evaluating Automotive Spark-Ignition Engine Fuel for
Electronic Port Fuel Injector Fouling by Bench Procedure
This standard is issued under the fixed designation D6421; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers a bench test procedure to evaluate the tendency of automotive spark-ignition engine fuel to foul
electronic port fuel injectors (PFI). The test method utilizes a bench apparatus equipped with Bosch injectors specified for use in
a 1985-1987 Chrysler 2.2 L turbocharged engine. This test method is based on a test procedure developed by the Coordinating
Research Council (CRC) for prediction of the tendency of spark-ignition engine fuel to form deposits in the small metering
clearances of injectors in a port fuel injection engine (see CRC Report No. 592).
1.2 The test method is applicable to spark-ignition engine fuels, which may contain antioxidants, corrosion inhibitors, metal
deactivators, dyes, deposit control additives, demulsifiers, or oxygenates, or a combination thereof.
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for
information only and are not considered standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. Specific precautionary statements are given throughout this test method.
NOTE 1—If there is any doubt as to the latest edition of Test Method D6421, contact ASTM International Headquarters. Other properties of significance
to spark-ignition engine fuel are described in Specification D4814.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4814 Specification for Automotive Spark-Ignition Engine Fuel
D5500 Test Method for Vehicle Evaluation of Unleaded Automotive Spark-Ignition Engine Fuel for Intake Valve Deposit
Formation
D5598 Test Method for Evaluating Unleaded Automotive Spark-Ignition Engine Fuel for Electronic Port Fuel Injector Fouling
2.2 ANSI Standard:
MC 96.1 American National Standard for Temperature Measurement Thermocouples
2.3 CARB Standard:
Test Method for Evaluating Port Fuel Injector (PFI) Deposits in Vehicle Engines
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.A0.01 on Gasoline and Gasoline-Oxygenate Blends.
Current edition approved Nov. 1, 2019April 1, 2020. Published November 2019April 2020. Originally approved in 1999. Last previous edition approved in 20182019 as
D6421 – 18.D6421 – 19. DOI: 10.1520/D6421-19.10.1520/D6421-20.
“A Program to Evaluate a Bench Scale Test Method to Determine the Deposit Forming Tendencies of Port Fuel Injectors,” available from Coordinating Research Council,
Inc., 5755 North Point Parkway, Suite 265, Alpharetta, GA 30022, http://www.crcao.org.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Available from California Air Resources Board, P.O. Box 2815, Sacramento, CA 95815. (Incorporated by reference in California Code of Regulations, Title 13, Section
2257.)
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6421 − 20
2.4 Clean Air Act Amendment:
Clean Air Act Amendments of 1990, Public Law 101–549, Title 1 – Provisions for Attainment and Maintenance of National Air
Quality Standards
3. Terminology
3.1 For general terminology, refer to Terminology D4175.
Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov.
D6421 − 20
3.2 Definitions:
3.2.1 base fuel, n—in automotive spark-ignition engine fuels, a material composed primarily of hydrocarbons that may also
contain oxygenates, anti-oxidants, corrosion inhibitors, metal deactivators, and dyes but does not contain deposit control or lead
additives. D5500
3.2.1.1 Discussion—
A jurisdiction may set limits on lead content from all sources.
3.2.2 deposit control additive, n—material added to the fuel to prevent or remove deposits in one or more of the engine fuel,
intake, and combustion systems. D5500
3.2.2.1 Discussion—
For the purposes of this test method, the performance of a deposit control additive is limited to the electronic port fuel injector
tip areas.
3.2.3 driveability, n—in vehicles equipped with internal combustion engines, the quality of a vehicle’s performance
characteristics under a range of conditions as perceived by the operator. D4814
3.2.3.1 Discussion—
The performance characteristicsoperating conditions may include cold starting and warm-up, acceleration, idling, and hot
starting.start. The performance characteristics may include engine hesitation, stumble, and stall. D4814
3.3 Definitions of Terms Specific to This Standard:
3.3.1 cycle, n—a 15 s pulsing period, followed by a 50 min heating period at 160 °C (320 °F), followed by a 10 min cool-down
period.
3.3.2 electronic port fuel injector (PFI), n—an electromechanical device used to control fuel flow in an internal combustion
engine.
3.3.3 fouling, v—formation of carbonaceous deposits on the pintle or metering surfaces of an electronic fuel injector, which
reduces fuel flow rate.
3.3.4 pintle, n—a needle-like metering device extending beyond the electronic fuel injector body that is part of an electronic fuel
injector, which controls flow rate and spray pattern.
3.3.5 test fuel, n—base fuel, with or without the addition of a deposit control additive, that is used for evaluation as described
in this test method.
4. Summary of Test Method
4.1 This test method describes a procedure for evaluating the formation of deposits in PFIs. The test method includes a bench
test procedure that has been shown to rapidly form deposits in fuel injectors and a procedure for determining resultant flow loss.
4.2 This test method uses a simulated fuel system consisting of a fuel pump, filter, pressure regulator, fuel rail, and fuel injectors.
A heat source is applied to the fuel injectors to simulate the hot-soak portion of the vehicle test (see Test Method D5598).
4.3 Each test begins with screened injectors that are known to foul. The tips of these four clean fuel injectors are placed in an
aluminum block. A stainless-steel internal reservoir is filled with 2 L of the test fuel.
4.4 During one 60 min test cycle, the fuel injectors are pulsed for 15 s, followed by a 50 min hot-soak interval in which the
injector aluminum block temperature controller is set at a temperature of 160 °C (320 °F) and the fuel pressure is regulated to 263
kPa (38 psig), followed by a 10 min cool-down period. Flow measurements for each of the injectors are taken at the beginning of
the test, after 22 cycles, and at the end of the test at 44 cycles.
4.5 The change in the rate of flow for each injector from the start to the end of the test is used to determine the fouling
percentage of each injector.
5. Significance and Use
5.1 Driveability problems in PFI automobiles were first reported in 1984. Deposits are prone to form on the metering surfaces
of pintle-type electronic fuel injectors. These deposits reduce fuel flow through the metering orifices. Reductions in metered fuel
flow result in an upset in the air-fuel ratio, which can affect emissions and driveability. When heavy enough, these deposits can
lead to driveability symptoms, such as hesitation, hard starting, or loss of power, or a combination thereof, that are easily noticed
by the average driver and that lead to customer complaints. The mechanism of the formation of deposits is not completely
understood. It is believed to be influenced by many factors, including driving cycle, engine and injector design, and composition
D6421 − 20
of the fuel. The procedure in this test method has been found to build deposits in PFIs on a consistent basis. This procedure can
be used to evaluate differences in base fuels and fuel additives. A study of PFI fouling was conducted in both the bench test and
the vehicle test procedures to obtain a correlation. The vehicle tests were conducted as described in Test Method D5598. The tests
were conducted on several base gasolines, with and without additives blended into these base fuels. The PFI bench test proved to
be reliable, repeatable, and a good predictor of PFI fouling in test vehicles.
5.1.1 State and Federal Legislative and Regulatory Action—Legislative and regulatory activity, primarily by the state of
California (see 2.3) and the federal government (see 2.4), necessitate the acceptance of a standard test method to evaluate the PFI
deposit-forming tendency of an automotive spark-ignition engine fuel.
5.1.2 Relevance of Results—The operating conditions and design of the laboratory apparatus used in this test method may not
be representative of a current vehicle fuel system. These factors must be considered when interpreting results.
5.2 Test Validity:
5.2.1 Procedural Compliance—The test results are not considered valid unless the test is completed in compliance with all
requirements of this test method. Deviations from the parameter limits presented in Section 10 will result in an invalid test.
Engineering judgment shall be applied during conduct of the test method when assessing any anomalies to ensure validity of the
test results.
6. Apparatus
7,8
6.1 Automatic Electronic PFI Bench Test Apparatus —This apparatus is composed of two units, a fuel handling unit and a
controller.
6.1.1 Fuel Handling Unit—This unit houses a machined aluminum fuel rail and a heated aluminum block designed to
accommodate four PFIs. Heaters and thermocouples are mounted in the heated aluminum block. This unit also houses a 2.25 L
stainless steel reservoir, an electric fuel pump, a fuel regulator, and a variety of valves used to transfer fuel to and from the reservoir
and to deliver fuel under pressure to the injectors (see Annex A1).
6.1.2 Programmable Microprocessor Controller or Other Controller—The controller is used to fill the fuel reservoir, control
and measure the temperature of the heated block, pulse the injectors, control the soak period, count the number of test cycles, and
control the flow period for the measuring of the flow rate. The unit is programmed to shut down automatically at the end of each
22-cycle period.
6.1.3 External Pressure Regulator—This regulator is used to adjust the pressure of the nitrogen gas on the fuel system. This
ensures that the pressure of the fuel in the fuel rail is maintained with an accuracy of 66.8 kPa (61.0 psi) during the test.
8,9
6.1.4 Electronic PFIs—Only Bosch EV1.1A (Part Number 0280150360) pintle-style injectors shall be used. The correspond-
ing Chrysler Corp. part number is 4306024 and is clearly marked on the injector. The protective cap shall be removed from the
injector by cutting the plastic cap with a razor blade and gently heating with a heat gun. The rubber o-rings and spacers shall be
removed to expose the bare metal injector tip. Each injector shall be screened for fouling capability prior to use in the procedure.
The screening procedure is found in Annex A2.
6.2 Testing Area—The ambient atmosphere of the testing area shall be reasonably free of contaminants. The temperature should
be maintained at 24 °C 6 5 °C (75 °F 6 9 °F). Uniform temperature is necessary to ensure repeatable injector flow measurements.
The specific humidity shall be maintained at a uniform comfortable level. (Warning—Provide adequate ventilation and fire
protection in areas where flammable or volatile liquids and solvents, or both, are used. Suitable protective clothing is
recommended.)
6.3 Laboratory Equipment:
6.3.1 Analytical Balance—An analytical balance capable of 0.01 g resolution with a maximum capacity of at least 200 g is
recommended. The balance should be calibrated following the manufacturer’s procedure and frequency recommendations.
6.3.2 Graduated Cylinders—Four graduated cylinders of 50 mL or 100 mL capacity, accurate to the nearest millilitre are
recommended for use in flow testing.
6.3.3 Low Voltage Power Supply—A 12 V, variable, direct current power source should be used in cleaning of the injectors.
6.3.4 Ultrasonic Bath—An ultrasonic bath with heating capabilities should be used for the cleaning of the injectors.
6.3.5 Pipette Bulb—A pipette bulb should be used to draw injector cleaning solution into the injector for cleaning.
6.3.6 Pipette—A disposable transfer pipette should be used to fill injectors with the cleaning solution during the cleaning
procedure.
6.3.7 Plastic Disposable Beakers—Disposable plastic beakers of approximately 150 mL or other containers of equivalent size
should be used to contain the injector cleaning fluid during the clean up of the injectors.
The following instrument has been found suitable by interlaboratory cooperative testing: Port Fuel Injector Bench Test Apparatus. Available from Southwest Research
Institute, San Antonio, TX.
If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a
meeting of the responsible technical committee, which you may attend.
The sole source of supply of the pintle-style injectors known to the committee at this time is Robert Bosch Corp., 25th Ave., Broadview, IL 60153.
D6421 − 20
6.4 Data Acquisition—A data acquisition device, capable of collecting the raw data in accordance with 10.4, shall be required.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be used for all test procedures. Unless otherwise noted, it is intended
that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used provided it is first ascertained that the reagent is of sufficient purity
to permit its use without lessening the accuracy of the determinations.
8,11
7.2 Berryman Chem-Dip Carburetor and Parts Cleaner —This cleaner has been found effective in removing the deposits
built up in the injectors. This cleaner or any other carburetor or engine parts cleaner that is proven effective in removing such
deposits shall be used to clean the injectors. (Warning—Berryman Chem-Dip contains methylene chloride, monochlorotoluene,
xylene, ethyl phenols, and xylenols that are extremely dangerous if inhaled, are skin irritant on contact, and are carcinogenic.)
7.3 Rinsing Solvent—A 1:1 mixture of isooctane and xylene, or suitable mixture of solvents, shall be used to rinse the bench
test apparatus reservoir, injectors, and fuel lines between tests. Approximately 1 L is used.
7.4 Test Fuel—A test fuel is either a base fuel or a homogeneous blend of additives and base fuel. A single batch shall be blended
before the start of the test. Approximately 8 L (2 gal) of fuel is needed for a single test.
7.5 Additive/Base Fuel—Some test requestors may require that the test fuel be blended at the test laboratory and, therefore, will
supply the deposit control additive and may, at their option or if a suitable base fuel is not available at the test laboratory, supply
untreated base fuel. The test requestor shall supply the deposit control additive and, if supplied, the base fuel in appropriate
volumes and packaging to ensure safe and efficient handling. Blending instructions detailing the concentration ratio either
volumetric-based or mass-based shall accompany all deposit control additives. Mass-based measurement is preferred. The blended
fuel shall be clearly identified.
7.5.1 Additive/Base Fuel Shipment and Storage—The additive shall be shipped in a container as dictated by safety and
environmental regulations. The additive shall be stored in accordance with all applicable safety and environmental regulations.
7.5.2 Base Fuel—The base fuel used for this test method should be typical of commercial, automotive spark-ignition engine
fuel. The base fuel may contain oxygenates typical of those being used commercially.
7.6 Nitrogen Gas (≥99.9 % Pure)—This gas shall be used to pressurize the fuel system and the fuel rail.
8. Preparation of Apparatus
8.1 Fuel Injector Preparation:
8.1.1 The injectors shall be cleaned (see A3.2) prior to the running of the test. Proper cleaning is essential for running a valid
test.
8.1.2 Check the injector flow (see A3.5). Injectors shall meet the conditions of Annex A4 before beginning the test.
8.2 Place the injectors into the fuel handling unit (see A3.3).
8.3 Pressurize the tank and the fuel lines with nitrogen gas.
8.4 Set test parameters as specified in Table 1. If using a programmable controller, program the controller in accordance with
A3.4, or refer to your manufacturer’s manual.
8.4.1 The test will run for 44 cycles with measurements taken at the end of each 22-cycle segment.
8.5 Add fuel to the internal fuel reservoir (see A3.5).
TABLE 1 Testing Parameters
Test Parameter Setting
Mode selection Constant pressure
Number of cycles 22
Pulse time 15 s
Soak time 60.00 min
Flush time 10 s
Fill time 0 s to 99 s
Base temperature 160 °C
Cool time 10 min
Flow time 12 s
Injector mode All at once
ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference Materials, American Chemical Society, Washington, DC. For
suggestions on the testing of reagents not listed by the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and
the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
The sole source of supply of the cleaner known to the committee at this time is Berryman Co., Dallas, TX.
D6421 − 20
9. Procedure
9.1 Mount screened and cleaned injectors into the fuel handling unit and fasten in place (see A3.3).
9.2 Ensure that test parameters are set in accordance with Table 1 and that all other steps in Section 8 have been completed.
9.3 Measure the initial or pre-test injector flow (see A3.6).
9.3.1 Prior to making the measurement, bleed off any gases in the fuel rail (see A3.6) and discard the fuel.
9.3.2 Measure the flow masses for the four injectors independently. Hold the injector pintle open for 12 s while subjecting fuel
to an initial nitrogen pressure of 263 kPa (see 6.1.3).
9.3.3 Record and average three separate flow mass measurements for each injector.
9.4 Begin test.
9.5 After completing 22 cycles, allow the base (aluminum block) temperature to cool to 24 °C 6 3 °C (75 °F 6 5 °F). The flow
measurement (see A3.6) shall be performed within 4 h of completing 22 cycles and with the same test fuel used for the pretest flow.
Record flow measurement results (see A3.6) and the base temperature at which the flow measurements were generated.
9.6 The test may be aborted at this point if the test parameters detailed in 10.4 have been compromised, or if any equipment
malfunction has been detected. Otherwise, continue testing for an additional 22 cycles.
9.7 After 44 cycles have been completed, allow the base temperature to cool to 2424 °C 6 3°C (753 °C (75 °F 6 5°F).5 °F).
Perform the flow measurement within 4 h of test completion and with the same test fuel as used for the pretest flow. Record flow
measurement results (see A3.6) and the base temperature at which the flow measurements were generated.
10. Calcula
...