Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G2500, VAN CARGO EXTENDED, 5.7 R, L31/KL8REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 72 (ENGINE CONTROL SYSTEM TESTING & ENGINE COMPONENT TESTING)FUEL SYSTEMS (2.2L - CAVALIER CNG)FUEL SYSTEM DIAGNOSISTEST DESCRIPTION
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8
Test Description
2001 Chevrolet Chevy Express G2500, Van Cargo Extended, 5.7 R, L31/KL8SECTION Test Description
WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2002 Saturn SL2, 2002 Saturn SL1, 2002 Saturn SL, 2002 Saturn SC2, and 2002 Saturn SC1. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers in the diagnostic procedures.
- 3
This step tests the fuel pressure output of the High Pressure Regulator (HPR). - 5
This step tests the fuel pressure output of the Primary Stage of the Low Pressure Regulator (LPR). - 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).
- 8
This step tests for the sound of a functioning LPL. A circuit failure to solenoid should set a DTC. - 9
This step tests for the sound of a functioning HPL. A circuit failure to solenoid should set a DTC. - 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. - 11
This step inspects for a closed manual lock-down screw. - 12
This step inspects for damage to the fuel line between the HPL and the LPR. - 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. - 20
This step tests for proper operation of the system after repairs are complete.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.