Fuel pump capacity test
Before performing this test, verify fuel pumppressure. Refer to Fuel Pump Pressure Test.
Use this test in conjunction with the Fuel PressureLeak Down Test.
(1) Release fuel system pressure. Refer to FuelPressure Release Procedure.
(2) Disconnect fuel supply line at fuel rail. Refer toQuick-Connect Fittings. Some engines may requireair cleaner housing removal before line disconnection.
(3) Obtain correct Fuel Line Pressure Test AdapterTool Hose. Tool number 6539 is used for 5/16" fuellines and tool number 6631 is used for 3/8" fuel lines.
(4) Connect correct Fuel Line Pressure TestAdapter Tool Hose into disconnected fuel supply line.
Insert other end of Adaptor Tool Hose into a graduatedcontainer.
(5) Remove fuel fill cap.
(6) To activate fuel pump and pressurize system,obtain DRB scan tool and actuate ASD Fuel SystemTest.
(7) A good fuel pump will deliver at least 1/4 literof fuel in 7 seconds. Do not operate fuel pump forlonger than 7 seconds with fuel line disconnected asfuel pump module reservoir may run empty.
(a) If capacity is lower than specification, butfuel pump can be heard operating through fuel fillcap opening, check for a kinked/damaged fuel supplyline somewhere between fuel rail and fuelpump module.
(b) If line is not kinked/damaged, and fuel pressureis OK, but capacity is low, replace fuel filter/fuel pressure regulator. The filter/regulator may beserviced separately on certain applications. Referto Fuel Filter/Fuel Pressure Regulator Removal/Installationfor additional information.
(c) If both fuel pressure and capacity are low,replace fuel pump module assembly. Refer to FuelPump Module Removal/Installation.
Fuel pressure leak down test
Use this test in conjunction with the Fuel PumpPressure Test and Fuel Pump Capacity Test.
Check Valve Operation: The electric fuel pumpoutlet contains a one-way check valve to prevent fuel flow back into the tank and to maintain fuel supplyline pressure (engine warm) when pump is not operational.
It is also used to keep the fuel supply linefull of gasoline when pump is not operational. Afterthe vehicle has cooled down, fuel pressure may dropto 0 psi (cold fluid contracts), but liquid gasoline willremain in fuel supply line between the check valveand fuel injectors. Fuel pressure that hasdropped to 0 psi on a cooled down vehicle(engine off) is a normal condition. When the electricfuel pump is activated, fuel pressure shouldimmediately (1-2 seconds) rise to specification.
Abnormally long periods of cranking to restart ahot engine that has been shut down for a shortperiod of time may be caused by:
- Fuel pressure bleeding past a fuel injector(s).
- Fuel pressure bleeding past the check valve inthe fuel pump module.
(1) Disconnect the fuel inlet line at fuel rail. Referto Fuel Tubes/Lines/Hoses and Clamps in this sectionof the group for procedures. On some engines, aircleaner housing removal may be necessary beforefuel line disconnection.
(2) Obtain correct Fuel Line Pressure Test AdapterTool Hose. Tool number 6539 is used for 5/16" fuellines and tool number 6631 is used for 3/8" fuel lines.
(3) Connect correct Fuel Line Pressure TestAdapter Tool Hose between disconnected fuel lineand fuel rail (Fig. 8).
(4) Connect the 0-414 kPa (0-60 psi) fuel pressuretest gauge (from Gauge Set 5069) to the test port onthe appropriate Adaptor Tool. The DRB III ScanTool along with the PEP module, the 500 psipressure transducer, and the transducer-to-testport adapter may also be used in place of thefuel pressure gauge.
The fittings on both tools must be in goodcondition and free from any small leaks beforeperforming the proceeding test.
(5) Start engine and bring to normal operatingtemperature.
(6) Observe test gauge. Normal operating pressureshould be 339 kPa 6 34 kPa (49.2 psi 6 5 psi).
(7) Shut engine off.
(8) Pressure should not fall below 30 psi for fiveminutes.
(9) If pressure falls below 30 psi, it must be determinedif a fuel injector, the check valve within thefuel pump module, or a fuel tube/line is leaking.
(10) Again, start engine and bring to normal operatingtemperature.
(11) Shut engine off.
(12) Testing for fuel injector or fuel rail leakage:Clamp off the rubber hose portion of AdaptorTool between the fuel rail and the test port "T" onAdapter Tool. If pressure now holds at or above 30psi, a fuel injector or the fuel rail is leaking.
(13) Testing for fuel pump check valve, filter/regulator check valve or fuel tube/line leakage:Clamp off the rubber hose portion of Adaptor Toolbetween the vehicle fuel line and test port "T" onAdapter Tool. If pressure now holds at or above 30psi, a leak may be found at a fuel tube/line. If noleaks are found at fuel tubes or lines, one of thecheck valves in either the electric fuel pump or filter/regulator may be leaking.
Note: A quick loss of pressure usually indicates adefective check valve in the filter/regulator. A slowloss of pressure usually indicates a defective checkvalve in the electric fuel pump.
The electric fuel pump is not serviced separately.
Replace the fuel pump module assembly. The filter/regulator may be replaced separately on certainapplications. Refer to Fuel Filter/Fuel Pressure RegulatorRemoval/Installation for additional information.
Fig. 8 Connecting Adapter Tool-Typical
1 - VEHICLE FUEL LINE
2 - TEST PORT "T"
3 - SPECIAL TOOL 6923, 6631, 6541 OR 6539
4 - FUEL PRESSURE TEST GAUGE
5 - FUEL LINE CONNECTION AT RAIL
6 - FUEL RAIL
Fig. 8 Connecting Adapter Tool-Typical