Fuel Pump Functional Tests

NOTE: The following test procedures assume that the ignition system is functioning, and that a good spark is present at the spark plugs. If this is not the case, diagnose and repair any ignition problems before proceeding with fuel system testing.
1. If vehicle runs but has a DRIVEABILITY complaint go to step 4.
2. Remove air cleaner housing, disconnect coil wire from distributor and ground the loose end of wire.
3. Observe the fuel injector while cranking the engine for at least 7 seconds.
^ If the injector is spraying an excessive amount of fuel test the injector and pressure regulator. Fuel System Diagnosis
^ If there appears to be a normal amount of fuel being sprayed by the injector, and there is a good spark but the engine does not start, check valve timing as timing belt may have slipped.
^ If no fuel is being sprayed by the injector, go to step 4.

Fuel Pressure Release:

4. Loosen fuel tank filler cap to relieve fuel tank pressure. Disconnect injector wiring harness at injector and connect a jumper wire from one terminal of the injector side of the connector to ground. Connect a second jumper wire to the other terminal of the connector, and touch this wire to the positive battery post for 10 seconds while observing the injector for evidence of fuel pressure release.
^ If there was no evidence of fuel pressure release, and there was no spray from the fuel injector when cranking the engine, test Auto Shut Down (ASD) relay operation.
^ If fuel pressure was evident and there was no spray from the injector during cranking, check the injector circuit. Testing and Inspection
^ If fuel pressure was evident and there was normal spray from the injector go to step 5.
5. Carefully remove 5/16 fuel supply hose from the engine fuel line assembly and connect fuel pressure gauge C-3292, and hose adapter C-4799 or equivalents between supply hose and fuel line assembly

Fuel Pressure Testing Equipment:

6. Using the appropriate tester (DRB II or equivalent scan tool), place ignition switch in "RUN" position and use Actuate Output Test "Auto Shutdown (ASD) Relay", to activate fuel pump and pressurize system. This test will activate the fuel pump for 1.5 second intervals. (listen for hum from fuel tank area). The gauge should read 100 kPa plus or minus 7 kPa, (14.5 psi plus or minus 1 psi).
^ If fuel pressure is below 93 kPa (13.5 psi) proceed to step 7.
^ If fuel pressure is above 111 kPa (16.0 psi) proceed to step 9.
^ If pressure is as specified the fuel system is operating correctly and no further testing is necessary.
7. If fuel pressure is below specification, move pressure gauge to fuel supply line and install between fuel tank and fuel filter. Repeat test procedure, and check fuel system pressure.
^ If pressure is 5 psi higher than previous reading and within specification, replace fuel filter. Service and Repair
^ If no change occurs in pressure proceed to step 8.
8. Gently squeeze fuel return hose.
^ If pressure increases to specification replace fuel pressure regulator. Service and Repair
^ If no change in pressure occurs, replace the in tank pump and sock type filter. Service and Repair
9. If fuel pressure is above 111 kPa (16.0 psi) remove fuel return hose from fuel pressure regulator end, and install a suitable hose from fuel pressure regulator output. Place the other end of the hose in a large (2 gallon minimum), clean and approved container. START engine and observe fuel pressure.
^ If pressure is now within specification, problem is a restriction in fuel return line, or an obstructed fuel return check valve in tank. Clear return line obstruction if necessary, and/or replace fuel tank assembly if in-tank check valve is obstructed.
^ If pressure is still above specification replace fuel pressure regulator. Service and Repair