Fuel Issues - Pump or Relay

OUMike · December 21, 2004

A little background. I have a 1994 Silverado with the 4.3L TBI motor. Over the past few weeks I'll have trouble starting it early on, but when it does start it runs fine. I've never had a drop off in MPG and it doesn't run rough. When I say trouble starting, sometimes it would take a few more cranks to get it goin'. A few days ago it wouldn't start..at all. The motor would crank over and over again, but never start the motor. Upon further inspection we learned the fuel pump wasnt' building any pressure before the motor turned on. I pulled the air breather off to see if gas was spraying from the injectors....nothing. At that point we called it a day and diagnosed the problem as a bad fuel pump.

After a little time thinking about it and looking inside the engine compartment I noticed on the firewall there are two things that caught my eye. FUEL PUMP RELAY and FUEL PUMP FUSE. Now for the question. Has anyone ever expirenced a simialar problem that was solved by changing these fuses? I'd definatly rather replace a fuse and relay before dropping my gas tank and pulling the pump.

I think it could be the relay for a few reasons. 1) The truck never runs rough when it does start. 2) I would think that if the pump was bad, I would see some movement in my mileage one way or the other. Again..no change in its performance. Another thing I'd heard is that some of the trucks have an "inirtia switch" that acts as a fuel cut off, but I was told that GM trucks of this age were not equiped which such an animal.

As usual, any feedback is welcome and appriciated. Thanks guys

Shawn T · December 21, 2004

I had a problem years ago on my 88 TBI. Same problems you are having. It seems to me that there was not an "inertia switch" but a primitive type of idle control module. I think it was an actual control valve. I'm not posative but, I know it was something on the intake that controlled the fuel volume at start up. I know this because I changed the pump and it did not remedy the problem. My buddy was a knowledgable mechanic and he remedied the problem right away. It was bleeding off overnight causing rough start-ups but it ran fine after that. Like I said, I am not sure but maybe someone will read this reply and know for sure what I am trying to explain. Good luck!

budhayes3 · December 21, 2004

From my experience, the pump's are more common than the relay, although it couldn't hurt to check. If the fuse was bad, it wouldn't run at all. You can check the connections at the relay and fuse, maybe even swap the relay if there's another one in there like it. One way to check is to tap on the relay while someone is cranking, or whack the gas tank while cranking...whichever one allows the vehicle to start or sputter is most likely your problem.