Test Description

The numbers below refer to the step numbers in the diagnostic procedures.

1. 3
   
   This step tests the fuel pressure output of the High Pressure Regulator (HPR).
2. 5
   
   This step tests the fuel pressure output of the Primary Stage of the Low Pressure Regulator (LPR).
3. 6
   
   CNG fuel may contain small amounts of fill station compressor oil. As the CNG fuel pressure drops in the LPR secondary chamber this oil separates from the CNG fuel and collects in the secondary chamber. Allow the oil to drain as this condition is normal and no repair is required.

   This step tests the fuel pressure output of the Secondary Stage of the Low Pressure Regulator (LPR).

4. 8
   
   This step tests for the sound of a functioning LPL. A circuit failure to solenoid should set a DTC.
5. 9
   
   This step tests for the sound of a functioning HPL. A circuit failure to solenoid should set a DTC.
6. 10
   
   This step tests for a restricted High Pressure Regulator (HPR) filter. If a restricted HPR filter is found also inspect the fill valve filter for contamination, damage or restriction.
7. 11
   
   This step inspects for a closed manual lock-down screw.
8. 12
   
   This step inspects for damage to the fuel line between the HPL and the LPR.
9. 19
   
   This step tests for a leaking LPL. A leaking LPL would allow CNG fuel to enter the engine after the ignition has been turned OFF. The leaking LPL could cause a hard or no-start condition during the next ignition cycle. A leaking LPL would cause the gauge to indicate fuel pressure for up to several minutes after the ignition has been turned OFF.
10. 20
    
    This step tests for proper operation of the system after repairs are complete.