Can someone give me serious, usefull help?

Asked by May 07, 2015 at 01:50 AM about the 1991 GMC S-15 Jimmy 4 Dr SLE SUV 4WD

Question type: Maintenance & Repair

I'm driving through town at about 20+, when my '91 GMC Jimmy suddenly acts like it's out of gas. I manage to get home by constantly pumping the gas pedal. Having this very same thing happen twice before when I ran out of gas, I put in 5 gallons to get to a gas station, and the truck restarted and ran good as usual. But as I again came through town heading home, it again acted like it was out of gas and I had to keep pumping the gas to get home. Now I'm thinking the fuel pump is shot and I have to pull the tank and so on. But before I have to go that route, I try replacing other parts first. I put in a new fuel filter (old one was still clean like new)...nothing changed. I replaced the TPS valve on the TBI unit. Nope...truck still acts up. Now, all this time I notice, that when first turning on the key, I nolonger here a slight click, click buzz from under the hood or in the fuel tank like before. But....if I put my ear to the filler tube to the fuel tank or get under the tank, I can hear the fuel pump and the gas gurgling through the line! I also notice, that when cold, the engine nolonger has a high, choke induced idle like it used to do. Ok...to today's work....I then replaced fuel pump relay, and remove the top to the TBI to check the diaphragm for tears or leakage in the fuel regulator. Everything ok there. Restart truck, it starts right up and I can rev it to 2 grand+ for a few seconds, then it starts to die down to where it has a very rough, pulsating idle, or no idle at all. I did wiggle a connection at the temperature gauge connection and it ran better for a few seconds, then went back to it's rough, pulsating idle. Then on a whim, I pulled the connection on the oil pressure switch and it began running like a new truck again, until I let off the gas. Then it idled at 800 RPM like it regularly used to do. But stepping on the gas, then killed the motor, and figured there was no gas because the fuel pump get s it's power from the oilpressure switch! Reconnected the oil pressure wires, restarted the truck and it ran with the original sputtering and having to keep pumping the gas to make it run. If this was an older vehicle with a carb, I'd swear it had sudden mass vacuum leaks. But every hose is new and tight. What gives!

1 Answer

261,805

Did you check the fuel pressure yet to verify the pump is weak?

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