Circuit/System Testing

Fuel Pressure Low

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

     Repair as necessary.

   • If no conditions exist 

     Replace the G12 Fuel Pump.

Fuel Pressure Leaks Down

1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief (High Side) .
2. Install the EN37287  Adapter between the chassis fuel feed hose and the engine compartment fuel feed pipe.
3. Open the valve on the EN37287  Adapter.
4. Ignition ON, command the Fuel Pump Enable On with a scan tool and bleed the air from the CH48027  Gauge.
5. Command the Fuel Pump Enable On and then Off with a scan tool.
6. Close the valve on the EN37287  Adapter.
7. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 min.
   • If greater than 34 kPa (5 psi) 

     Locate and replace the leaking Q17 Fuel Injector.

   • If less than 34 kPa (5 psi) 

     Replace the G12 Fuel Pump.

Fuel Pressure Drops Off

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

     Repair as necessary.

   • If no conditions exist 

     Replace the G12 Fuel Pump.