Circuit/System Testing

Fuel Pressure Low

1. Verify none of the conditions listed below exist:
   • Restricted fuel feed pipe
   • Restricted or plugged strainer
   • Poor connections at the fuel pump harness connector and the ground circuits.
   • If a condition exist 

     Repair as necessary.

   • If none of the conditions exist 
2. Test or replace the G12 Fuel Pump.

Fuel Pressure Leaks Down

1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief .
2. Install the J 37287  Fuel Line Shut-Off Adapter between the fuel feed pipe and the fuel rail.
3. Open the valve on the J 37287  Fuel Line Shut-Off Adapter.
4. Ignition ON, command the Fuel Pump Enable ON with a scan tool and bleed the air from the fuel pressure gauge.
5. Close the valve on the J 37287  Fuel Line Shut-Off Adapter.
6. Verify that the fuel pressure does not decrease greater than 34 kPa (5 psi) in 1 minute.
   • If the fuel pressure drops 

     Locate and replace the leaking Q17 Fuel Injector, refer to Fuel Injector Diagnosis Fuel Injector Diagnosis (LSA) 

   • If the fuel pressure does not drop 
7. Test or replace the G12 Fuel Pump.

Fuel Pressure Drops OFF

1. Verify none of the conditions listed below exist:
   • Restricted fuel feed pipe
   • Restricted or plugged strainer
   • Poor connections at the Fuel Pump harness connector and the ground circuit.
   • If a condition exist 

     Repair as necessary.

   • If a condition does not exist 
2. Test or replace the G12 Fuel Pump.