Having problems with your 1997 GMC Sierra ?

1997 GMC 1 ton 4x4 hard to start after it has warmed up. changed fuel filter no help No code to be read We have notice that the fuel in the rail is vapor not a liquid. Is this normal and if not what would be the cause. Fuel pump runs at 45 psi until it shut off then drops down to zero is this normal. Or should the pressure hold. If the fuel line is bead after the fuel filter the pump will hold at 45 psi during the bleeding.

Posted / edited by AnonymousUser on : 27-09-2021

Answers :

The fuel pressure should hold at or near the 45 lbs after you shut the truck off.
You have one of three problems causing this.
One, the fuel pressure regulator is leaking internally and allowing fuel to return to the tank via the return line. To verify, use a pair of pliers and gently pinch the return line off. Turn the key on to the run position, the pump will run for 2 to 5 seconds and pressurize the line. Watch the pressure gauge, it should hold pressure. If it does, change the regulator.

Two, the check valve at the pump is weak. To verify, turn the key to the run position, when peak pressure is reached, gently pinch the pressure line and watch the pressure gauge. If the pressure remains near the peak pressure the check valve is bad. Replace the fuel pump.

Three, if neither of the above procedures work, you have a leaking injector. You will want to remove the fuel rail, pressurize it to find the bad injector.

Any one of these failures will cause the "vapor" issue you describe.

Good luck, let me know what you find.
Regards,
Repair Help & Product Troubleshooting for 1997 GMC Sierra

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