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Working on a 99 GMC Jimmy 4.3 4WD did an engine swap on the jimmy got everything back together tried to start it and it cranks but doesn't start, however if I put fuel down the intake and crank it it will start and run. It is not throwing any codes so I am sort of at a loss as to wear to start the troubleshooting Any ideas out there?
Ok Turning the switch to the on position, fuel pressure is 55 psi. when cranking it drops to 40 psi. I can zero it out and turn the switch on and it jumps to 55 psi So to me this indicates the fuel pump is working. Shut the switch off and it starts to drop off. Am I correct in assuming this indicates a bad fuel regulator?
If my gauge is is showing 55 psi with the switch on but drops off when cranking is that not indicative of a bad fuel regulator?? The battery is new and my customer says there is a new fuel pump in the tank.
Fuel Pressure is low. Is your the SFI or CSI (spider injectors) ? Pinch off the return line switch key to on position and see if pump is strong enough to push the psi roughly 80-90 psi. If this pump passes this test, then change the regulator. Don't forget to change out the fuel filter while you're there.
