My 89 GMC Sierra c2500 won't start. I was driving home from school the other day and it started stumbling and running rough. When I came up to the light, it seemed like it was running smooth and when the light turned green, I started to accelerate and the truck stalled on me. It took me several starts to get it fired back up and I was able to drive it a couple blocks from my house before it stalled on me again. This time I couldn't get it started and I had to get help to push it across the intersection. I sat for a minute, got it started and drove it home at about 10 mph. Any faster and the truck would start to hesitate and stumble. I was able to coast the truck into my driveway and before I could even put the truck in park and turn the engine off, the engine stalled on me again. Now I can't even get the truck to start and idle. It turns over just fine and I have just purchased a brand new battery. I have also just replaced the fuel filter and the coolant temperature sensor. The only way I can get the truck to start is if I pour some gas directly into the carburetor. The engine will fire and run until it burns up the gas. Any ideas or suggestions on where to begin would be greatly appreciated. Thanks for your help!! BTW, I purchased this truck from my neighbor who was the original owner and took excellent care of the truck. That is the reason I purchased it from him as I know he has never had any problems with it. It has sat for about 6 months because he purchased a brand new 2010 GMC Sierra 2500 quad cab truck. How did I suddenly inherit all the problems? I've seen him drive the truck for 20 years with not one problem .

 

Sounds like a bad fuel pump. I would get the pressure checked.

 

yup. I agree with ShamRock

 

Well gentlemen, I took the truck in first thing this morning and sure enough it is a bad fuel pump and they also told me something about a bad harness. Could anyone shed any light on the harness? what exactly does that mean and how does it affect me?

thanks everyone.
Brady

 

The pump and sending unit assembly is located in the fuel tank. The harness provides 12volts to the pump. If the harness is corroded or damaged this will not provide battery +, or ground, thus causing loss of pump or intermittent pump operation. your mechanic suggested that to give you a chance to check it first before condemming the pump. My experience is its probably the pump. also easier to remove the truck box bolts and prop it up to remove the pump from the tank, opposed to spending hours removing the tank from the truck. Unless you have a car hoist in your tool box. good luck, let us know the outcome.

 

Did they actually inspect your harness? The "typical" harness issue was in the newer trucks - not to say that it is impossible for your harness to have gotten damaged somehow, but the ones I have replaced have been in the Vortec equipped trucks. Like already mentioned lifting the bed is a lot easier and the pumps for the 89 trucks are much less expensive than the newer ones. I put a pump in my brothers 89 GMC and we were done in less than 2 hours. Good luck man!

 

Good news everyone! It was just the fuel pump and I replaced it and the truck runs like a dream!! Thanks everyone for their help and input!! Very much appreciated!