Circuit/System Verification

NOTE:

Inspect the fuel system for damage or external leaks before proceeding.
Verify that adequate fuel is in the fuel tank before proceeding.
The Fuel Pump Relay may need to be commanded On a few times in order to obtain the highest possible fuel pressure.
Before proceeding with this test review the User Manual CH 48027-5 for Safety Information and Instructions.

Ignition ON.
Verify that the fuel pump turns ON and OFF when commanding the Fuel Pump Relay On and Off with a scan tool.
- If the fuel pump does not turn ON and OFF
  Refer to Fuel Pump Electrical Circuit Diagnosis .
- If the fuel pump does turn ON and OFF
Ignition OFF, all accessories OFF, install a J 42982 Fuel Pressure Gauge Adapter and a CH 48027 Gauge.
Ignition ON, engine OFF.
Command the Fuel Pump Relay On several times with a scan tool.
Verify the fuel pressure is between 276-345 kPa (40-50 psi) with the fuel pump running.
- If less than 276 kPa (40 psi)
  Refer to Circuit/System Testing - Fuel Pressure Low.
- If greater than 345 kPa (50 psi)
  Replace the G12 Fuel Pump.
- If between 276-345 kPa (40-50 psi)
Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
- If greater than 34 kPa (5 psi)
  Refer to Circuit/System Testing - Fuel Pressure Leaks Down.
- If less than 34 kPa (5 psi)
Relieve the fuel pressure to 69 kPa (10 psi).
Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 min.
- If greater than 14 kPa (2 psi)
  Replace the G12 Fuel Pump.
- If less than 14 kPa (2 psi)
Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH 48027 Gauge.
Verify the fuel pressure does not drop off during acceleration, cruise or hard cornering.
- If the fuel pressure drops off
  Refer to Circuit/System Testing - Fuel Pressure Drops Off.
- If the fuel pressure does not drop off
If the fuel system components test normal, refer to Symptoms - Engine Controls and Fuel Injector Diagnosis .