Circuit/System Testing

Fuel Pressure Low

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

     Repair as necessary.

   • If a condition does not 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 EN-37287  Fuel Line Shut-Off Adapters between the fuel feed pipe and the fuel rail.
3. Open the valve on the EN-37287  Fuel Line Shut-Off Adapters.
4. Ignition ON, command the Fuel Pump Enable On with a scan tool.
5. Close the valve on the EN-37287  Fuel Line Shut-Off Adapters.
6. Verify the Fuel Rail Fuel Pressure parameter does not decrease greater than 34 kPa (5 PSI) in 1 min.
   • If the fuel pressure drops 

     Replace the G12 Fuel Pump.

   • If the fuel pressure does not drop 
7. Locate and replace the leaking Q17 Fuel Injector.

Fuel Pressure Drops OFF

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

     Repair as necessary.

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