QuestionHello, I have a 1997 Chevy Cheyenne 1500 with a V6. It has almost 200,000 miles on it, and the fuel relay keeps going bad on it. The fuel pump has been replaced on it all ready once. Less then 5,000 miles ago. Before hand the relay would keep blowing, and we would replace it. Now with the new pump it, the problem still continues. I can't find a diagram to see if the relay is getting a higher Voltage then it should. Could you tell me if its a pump issue or possibly a short in the box, or possibly in the wiring thank you.
Answer Assuming that the new pump was the correct one, there is no good reason that the relay should be failing. I would be willing to bet that the pump was not installed correctly. Either in the tank or where the wiring goes to the pump on the outside, the hot wire to the tank has gotten pinched or somehow shorted. A lot of aftermarket replacement fuel pumps are sort of generic, and require some splicing and rewiring to get them to work. If one of these was used, then you may even have what amounts to a dangerous situation. Gasoline does not conduct electricity, so the submersion of the pump and its operation in the tank are considered relatively safe; in fact, the fuel in the tank helps to cool the pump and make it last longer. But, if there is a partial or intermittent short in the pump or its wiring, then you may have sparks in the tank when the fuel level is low. This is VERY dangerous, and has caused the explosion of several airliners (even though jet fuel is almost unflammable compared to gasoline). What you need to do is find out how many amps the fuel pump is drawing through the relay, and compare that to the specifications. It might even be a good idea to drive with the ammeter connected and located in the driver's compartment to see if the current draw occasionally exceeds the specification. You should also check to see that the relay is the correct one. If it is not an OE (GM) relay, then I would try one from the dealer. There is nothing wrong with aftermarket parts, I sold them for thirty years, but sometimes the listings are simplified or just wrong (especially the computerized listings used by almost all parts stores now; I could tell you stories) and using an original equipment part will allay that fear and set you on the right path to finding out what's wrong.
Oh, and that idea of getting too much voltage won't fly because there is only the 12V in the truck. Of course, if the internal voltage regulator in the alternator failed, then you could have a lot more voltage, but the relay would not be the first thing to fail (most likely the radio).
Something else has occurred to me, and I'll just put it out there. These V6 engines have a very peculiar constant-flow fuel injection system that is prone to failure and leakage. If the injector body is leaking, and the pressure never rises high enough to cause the pump to shut off, then the pump will run all the time. If this happens, the pump will get hotter than it should, draw more current than it should, and exceed the duty cycle of the relay, burning it out. Usually the symptoms of fuel-injection failure are others, like over-rich running and hard starting when hot, but it's something to look at (although I'd look at the wiring problems first, as they are more likely and easier and cheaper to address).
