jrhody

I have a 1998 Chevy Express 3500 Van 7.4 L. It runs (or ran) like a champ. The other day as I was cruising at 60mph it just flat out died on the highway. I could crank it over just fine. The Fuel pump was not making any sound. A couple times when I was really cranking, it fired and sounded like it was almost going to start, but it just wouldn't. Had it towed home.

So here is what I've tried so far:
-Borrowed computer from Napa, but no codes or anything came up (check engine light is not on)
-Replaced fuel filter
-Replaced fuel pump
-Replaced fuel pump relay

No changes at all. The fuel pump still doesn't even do that initial 5 or 10 second run when I turn the key on. Just dead silence.

It occurred to me that water might be in the fuel (though I don't know how). But wouldn't that make the van sputter and die?-not just immediately kill like what happened to me.

I can't think of any other important details to include. From reading on here, these are the things I could figure out to try.

jrhody

I just remembered that a couple months ago as I was driving with the cruise control on, I started to lose speed-like it was gradually decreasing my speed, but still maintaining some control. I think I had it set to 70 mph and it slowed to like 55 or something before I caught it. It has done this a few times, but I also still use it and it works.

I was not using it when this all happened.

loosebearing

Check fuses . Relay gets fuel pump going.. then pcm takes over.
Check see if your getting power to relay.
Maybe a ignition problem.

jrhody

Ok. I didn't think to check ignition. I was thinking ignition just related to starting the engine up, but that's wrong, now that I think about it. Thanks for the tip!

jrhody

I checked the Ignition fuses under the hood. There are 3 of them. All fine. I couldn't see any for ignition down under by the brake pedal in front of the door. I'm just wondering where else I would check. If it gets too technical with the electricity and using a multimeter, I'll get lost. I'm just learning about how all this works. I guess I might just pull every fuse and look at it. Some of the abbreviations denoted on the fuse panel legend are no help to me.

I'm just praying it's a stupid little fuse and an easy cheap fix.

RacerX

go back to the fuel tank and check fuel harness for power. You may need a partner.

1. turn the key to start listen for the relay to click and then the pump to whir. Do you hear the relay click?
Yes?
Do you hear the fuel pump whir? If no pump whir then check the harness at the tank for power. 12V.
No power then the PCM is where the problem is, if power then the fuel sending unit is bad.

No relay click? Then no signal to start from the PCM. Antitheft inhibitor could be in effect. PASSKEY Problem.

Find PCM behind the glove box and make sure connections are firm. Now there is a fuel run wire in the B part of the harness, I think a blue wire with you have to backprobe with the positive lead on the multimeter for voltage when you turn the car to the run position.
5V is good, 0v is bad. this is the wire that closes the FP Relay. 0V means the problem is in the steering column(Antitheft Controls). 5V means the system is perfectamundo.

jrhody

Thanks Racer. I'm going to look at it right now.
Question about using a multimeter. Do I ground the black probe and then use the red one to touch the pin in the harness? I just got it and I have never used one before.

jrhody

So update is I checked the gray wire (on my diagram says its the fuel pump power circuit) with the multimeter and it has current running through it. Now since its a new fuel pump and sending unit (attached inside the pump housing) would you say it is most likely the PCM?

rico

you are positive you hooked up the fuel pump wire on top of the fuel tank rite... check voltage with key on that wire above fuel filter if you have the tank already back in the van....my concern is your first problem that you had that is not repaired yet....but i do think racer is rite sounds like you have a passkey problem....put key in ignition turn one click does security light go out or stay lit....if it stays lit you can try and do a relearn on the security system...if it stays lit you have a passkey issue...dont get to far ahead of yourself yet try this first get back to me and i will help you i have a 99 van with the same motor.

jrhody

I tried what you said with the key. The "security" light goes out after a few seconds. I don't understand this pass key issue, but it occurred to me that about mid February I was away for work back in my hometown. I took the key fob remote off the key chain so I only had the key. long story, but I forgot it there so I haven't used it since. I don't lock it there and I leave the keys in the ignition, but am always scared I'll lock my keys in so I took it off for a safety measure. The remote hasn't been used in 3 or 4 weeks now. Could that have something to do with it?

Also, about the wire harness on the fuel pump, I have been over it and over it again. I just took out the wires thinking they were frayed and corroded somewhere. I bypassed the relay, fuses, etc and just ran a wire direct to the pump's power from the battery. The pump kicked on just fine and van started right up.

I also got a wire LAN tracker (sends a signal through the dead wire and a wand picks up the signal down the line.) I picked up the signal up at the relay. Is it possible the wire is damaged somewhere, but still good enough to let a little signal through, but not supply enough power to my fuel pump?