Fuel Pump Testing
NOTE:
For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS
article.
- Visually inspect entire fuel delivery system for leaks, damaged or kinked lines and hoses. Ensure battery is fully charged and fuses are okay. Ensure adequate fuel is available in fuel tank. Release fuel pressure. See FUEL SYSTEM PRESSURE RELEASE. Install fuel pressure gauge. With Key On Engine Off (KOEO) to activate pump, check and record fuel pressure. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS
article. Proceed to the appropriate step, as indicated:
- If fuel pressure is within specification, go to step 2).
- If fuel pressure is zero, go to step 5).
- If fuel pressure is low, go to step 11).
- If fuel pressure is high, go to step 12).
- Check fuel injectors. See FUEL INJECTORS. Crank or run vehicle. Using a mechanic's stethoscope, listen for regularly spaced operating sounds at each injector. If sound is present, check fuel injectors for flow and leakage. Clean or replace injectors as necessary.
- If injector operating sound is not present, check fuel injector resistance. See FUEL INJECTORS. If injectors are not within specification, replace as necessary. If injectors are within specification, check injector electrical connections for continuity to ECA. If no continuity exists in circuit, check for 12 volts at each injector lead.
- If voltage is not present at injectors, see Quick Test procedure in the appropriate TESTS W/CODES article. Faults in injector circuit should set a service code. If no service code has been set, see CIRCUIT TEST H, in the appropriate TESTS W/CODES article.
- If fuel pressure is zero, ensure battery is fully charged and key is off. Ground fuel pump lead at SELF-TEST connector. Using a jumper lead, ground FP terminal. See Fig 1 . Ensure connection is okay at pump/sender unit. Turn key on, leaving engine off. Listen for sound of fuel pump. If pump is running, go to next step. If it is not running, go to step 7).
- Check condition of high-pressure fuel filter. If filter is free of contamination check fuel pressure regulator, go to step 12). If filter is contaminated, replace filter and recheck system pressure as in step 1) procedure.
- Turn key off and disconnect fuel pump/sender connector. Set DVOM on 200-ohm scale. Measure resistance between pump ground at connector and chassis ground. If resistance is greater than one ohm, repair open circuit to ground. If resistance is not greater than one ohm, go to next step.
- Ensure key is off and battery is fully charged. Disconnect harness connector from pump/sender unit. Ground FP terminal at SELF-TEST connector. With KOEO and DVOM on 20-volt scale, measure voltage at Pump Power terminal of pump/sender connector. If voltage is greater than 10.5 volts, replace pump/sender assembly. If voltage is not as specified, go to next step.
- With KOEO, check voltage at fuel pump inertia switch. If voltage is greater than 10.5 volts at both inertia switch terminals, repair wire between inertia switch and pump. If voltage is not as specified, reset or replace inertia switch as necessary and go to next step.
- Ensure key is off and battery is fully charged. Ground FP terminal at SELF-TEST connector. With KOEO and DVOM on 20-volt scale, measure voltage at fuel pump relay (Brown wire). If voltage is greater than 10.5 volts at relay, repair Brown wire between fuel pump relay and inertia switch. If voltage is not as specified, check voltage supply to fuel pump relay and to terminal No. 1 at ECA. For additional circuit testing information see CIRCUIT TEST J in the TESTS W/CODES article.
- Ground FP terminal at SELF-TEST connector. Using a DVOM, check voltage at fuel pump terminal (Pink/Black wire). If voltage at fuel pump is within .5 volt of battery voltage, go to step 6). If voltage is not as specified, go to step 5).
- Check engine compartment for leaks and ensure engine produces normal engine vacuum. See FUEL PRESSURE REGULATOR test procedure.
CAUTION:
Inspect fuel system for leaks or damage before testing fuel pump.