91 2.8l v6 Fuel Pump randomly comes on

[Wilbo]

Hello, got some great help last time so hopefully I'll get a repeat on this one.

As the title says my fuel pump seems to randomly come on after I park the truck. New fuel pump and the truck runs good (knock on wood) two weeks now but my pump has a mind of its own. Now it behaves normaly when I start and stop it. You can hear the pump come on for a few seconds then cut off when your about to start it. I changed the relay, there was 2 under the hood I changed the one with the orange wire and thought I had it fixed. Checked the truck for 3 days and it didn't come on but this morning it was running again.

I have to remove the battery cable every time I park it but it runs great (more knocking on wood) when I hook it back up.

A year or so ago I had something killing my battery never found out what is was but I replaced the key switch. That seemed to have fixed that issue Could there be something there causing the problem ? How much trouble would it be to replace the entire column? I've put 2 switches in it already and would just get something thats not worn out to replace the entire thing.

So any ideals? Whats the other relay for under the hood? Should both have been changed and are they the same?

[rutster]

I have one thing for you to check.

while the fuel pump is running with the engine off, locate your oil pressure switch, and unplug it.

If you have the schematics for the truck and look at the fuel pump circuit. you will notice the oil pressure switch on the ground side of the fuel pump relay. (it's a long story why chevy did this) but basicly oil pressure will turn on the fuel pump. if your pressure switch is going bad then this will keep your fuel pump running.

i know for a fact the late 80's and early 90's 4 cylinders in the s-10 had this feature. i'm pretty sure the 2.8l also had this.

let me know if this helps you out

[Wilbo]

I can't seem to find the schematics on the net anywhere. I'm gonna try to find a book with this stuff in it. Any paticular recommendations?

What is the second thing that looks identicle to the fuel pump relay? They are mounted side by side. They are even on the same little bracket?

[Wilbo]

Thought I'd give an update incase anyone searches for the same problem.

You where basically right rutster. Though it wasn't the switch itself it was the wires that plug into the switch.

As it turns out the wiring plug was bad, I finally went to change the switch and when I unplugged it the fuel pump came on. A bit of wriggling would cause it to turn on and off. So a trip to the junk yard to get a new old one. I also tested the connectors to make sure they weren't lose or broke with a continuity checker before I put it on. I also found that someone had already taped up bare wires further along the wiring and that the tape had hardened and came off. So I replaced the end and taped the heck out of it and used ties to keep the wires from touching anything that gets hot. So far it works good

So a bad connector, maybe not, now that I think of it but most assuredly bare wires wasn't helping the problem. Thanks for the reply rutster and sorry it took so long to get back with a reply I kinda got busy and just got around to messing with it.