ENGINE CRANKS BUT WON'T START (NGV - NATURAL GAS VEHICLES). GMC Truck GMC C Pickup

SUBJECT: NGV ENGINE CRANKS BUT WILL NOT START

MODELS: 1992 C1/C2 WITH NGV DEDICATED FUEL SYSTEMS

CONDITION

Some of the subject vehicles may experience one or more of the following symptoms:

1. Engine cranks but will not start. 2. No gas odor (near the TBI) during cranking. 3. No injector popping noise with throttle open while cranking.

NOTES:

1. Under NO CONDITION are you to check the fuel pressure with Kent-Moore J-21867 Universal Pressure Gauge or any other UNAUTHORIZED gauge for the above comments. 2. Leak testing should always be performed after any component is replaced.

DIAGNOSTIC AND REPAIR PROCEDURES

1. Verify electrical signal to the low pressure solenoid (key on, 12 V for 2 seconds). A. If O.K., go to #3. B. If not O.K., go to #2. 2. Diagnose for open or short in fuel supply circuit and be sure fuel fill door is shut. 3. If above checks are normal, with key off, loosen nut on inlet line to fuel pressure regulator, allowing pressure to bleed off (should take from 2-30 seconds depending on pressure in line). 4. Re-tighten the nut on the inlet line to fuel pressure regulator. 5. Turn ignition on and start engine. 6. If vehicle starts and runs, the fuel pressure regulator has allowed the fuel pressure to creep up and the pressure regulator valve must be replaced. 7. If the vehicle doesn't start, replace the low pressure cut-off solenoid.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.