Circuit/System Testing

Fuel Pressure Low

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

     Repair as necessary.

   • Go to next step : If no conditions exist 
2. Replace the G12 Fuel Pump.

Fuel Pressure Leaks Down

1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief .
2. Install the CH - 37287 - 1A  between the fuel feed pipe and the fuel rail.
3. Open both valves on the CH - 37287 - 1A  .
4. Ignition ON, command the Fuel Pump Enable ON with a scan tool.
5. Close one of the valves on the CH - 37287 - 1A  .
6. Verify that the Fuel Pressure Sensor parameter does not decrease greater than 34 kPa (5 PSI) in 1 minute.
   • If greater than 34 kPa (5 PSI) 

     Test or replace the G12 Fuel Pump.

   • Go to next step : If less than 34 kPa (5 PSI) 
7. Test for a faulty fuel feed front pipe check valve.
   • If a condition exists 

     Replace the fuel feed front pipe.

   • Go to next step : If no condition exists 
8. Test for a leaking G18 High Pressure Fuel Pump.
   • If a condition exists 

     Replace the G18 High Pressure Fuel Pump.

   • Go to next step : If no condition exists 

     Go to next step : Locate and replace the leaking Q17 Fuel Injector.

Fuel Pressure Drops OFF

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

     Repair as necessary.

   • Go to next step : If no conditions exist 
2. Replace the G12 Fuel Pump.