Fuel Pressure Test
- Ensure fuel tank has adequate fuel. Turn ignition off. Install fuel pressure gauge. Install a test lead to Fuel Pump (FP) lead of VIP test connector. See Fig 1 . Turn ignition on, engine off. Ground test lead to run fuel pump. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS . If fuel pressure is within specification, go to step 5). If fuel pressure is not within specification, go to next step.
- If pressure is low, but greater than 3 PSI (21 kPa), go to next step. If pressure is not more than 3 PSI (21 kPa) go to step 4).
- Check fuel system for:
- Plugged fuel filter (replace filter and check again for proper pressure).
- Kinked/restricted fuel lines (visual inspection).
- Low voltage to fuel pump (should be within 0.5 volt of battery voltage at connector).
- Disconnect return fuel line and note if fuel is being returned during this low pressure condition. If fuel is being returned, replace or adjust pressure regulator.
If a problem was found, repair as necessary. After repair, go to step 1) and retest system. If a problem was not found, replace fuel pump and go to step 1) and retest system.
- Check the following electrical circuit problems:
- Ensure inertia switch is not open (reset switch as required).
- Wiring at fuel pump/tank connector loose or open.
- Fuel pump ground connection at chassis loose or defective.
- Improper fuel pump relay operation (should operate when fuel pump test lead is grounded with the ignition key on).
- EEC relay not operating if fuel pump relay doesn't operate.
If a problem was found, repair as necessary. After repair, go to step 1) and retest system. If a problem was not found, replace fuel pump and go to step 1) and retest system.
- Remove ground from test lead and note pressure on gauge. Pressure should remain within 2 PSI (14 kPa) for 3 minutes after lead is ungrounded. If pressure holds as specified, go to step 7). If pressure does not hold as specified, go to next step.
- Check fuel lines and connectors for leakage. Disconnect fuel return line and plug engine side. Momentarily activate fuel pump by grounding test lead. Raise pressure to approximate operating pressure and repeat step 5). If pressure holds, replace pressure regulator and repeat step 5). If a problem was found and repaired, go to step 1) and retest system. If a problem was not found, replace fuel pump and go to step 1) and retest system. If system still fails step 5), there may be a leaking fuel injector or rail. Repair as necessary and go to step 5).
- Disconnect and plug vacuum line connected to the pressure regulator. Start engine and run at idle. Check fuel pressure. See FUEL PRESSURE SPECIFICATIONS . If fuel pressure is within specification, go to step 9). If fuel pressure is not within specification, go to next step.
- Check the following for cause of low pressure:
- Fuel filter restriction.
- Improper fuel regulator adjustment.
- Fuel line restricted.
- Improper voltage to fuel pump (battery voltage at pump connections).
If a problem was found, repair as necessary. After repair, go to step 1) and retest system. If a problem was not found, replace fuel pump and go to step 1) and retest system.
- With engine running at idle and vacuum line disconnected, note fuel rail pressure. Rapidly accelerate engine and watch fuel pressure. If pressure remains within 5 PSI of starting pressure, system is okay. If pressure does not remain within 5 PSI of starting pressure, go to step 8).
NOTE:
Road testing vehicle while monitoring pressure may give a better test under load conditions.