Chevy & GMC Vans

I know my 99 has it in the fuse box in the engine bay. no clue where it is on my 93... or if there's a fuse that might be going bad...

first off, what are the chances I have two fuel pumps go in two vans within two weeks??? LOL

here's the problem. no start. turns over great. when it did get running the check engine light would flicker and the van was running really rough. after sitting a week, now it's a no start. cranks great, new battery etc.

i figured, cap, rotor, coil, etc etc... I pulled the coil wire, great spark. then i listened for the fuel pump hum. nada.

turned key between on/off position a few times but didn't go as far as cranking it. i'm leaning on the passenger seat with the doghouse off and after about 30 secs i hear hum hum hummmmmmm... i jump at the key crank it and it fires right up. bogs a couple of times, dies. hammered the tank.. nothing. no humm and couldn't get it to do it again...

oh ya, reason that I would think relay or fuse instead of pump itself: why would the pump try and engage 20 - 30 sec after the key was in the on position? should it not only engage when initially turned to the on position??

ideas? thanks

rob

I think I found the location of the relay. pass side firewall on a bracket. I'm going to have to see if I can swap it with another and see if any difference.

still wondering if anyone can confirm if/how the system works when the key is turned to the on position. I find it really weird that after the key was turned on and nothing happened 20 - 30 sec later the fuel pump hummed and pumped the fuel.

thanks

is there not another relay right beside it Rob? i believe you can try the other one to rule out whether the fuel relay itself is bad.

If you have a W engine (CPI) there will be another relay next to the fuel pump relay. It's for the variable orifice blah, blah. They are the same and can be swapped. Your AC one will be there too but it's bigger.

Sounds like your ECM is going bad.
Clue 1, The 'Check Engine' light is flickering....
Clue 2, The fuel pump is turning on 20 - 30 seconds later....

I recently ( Friday ) diagnosed a '93 Sunbird with very similar symptoms. Give your ECM a smack & see if that strightens it out - temporarily.

I will try both, swapping relays and whacking the ECM. it's currently at a friends place a few blocks from me, i'll stop on my way to work and see

1) how model specific are these GM ecm's? can I grab one at a wrecker from a 94, 95, 96 etc? or do I need another 93? does it matter if awd or not? etc.

2) can this be scanned and figured out, or the ol' pin jump to get codes? will there be an indication that the ecm is going south?

thanks

You must have one from a 93 or 94 with the same engine. Z or W. There are others you could use if you were swapping the chip but that may be what is wrong with yours.

thanks doc

i stopped in and checked out the relays. or what I think were the relays. a small one on the left and right and a large plug in the middle. i swapped the plugs between the two outer small ones. no change. just before i did that i turned the key once and did hear some random clicking.

i also gained access to the ecm and hammered on it's case with no result.

How are the ECM fuses? If one or both are blown, check the wire harness that goes from the ECM through the firewall near the doghouse cover. Once through the firewall, follow the wire harness to where it goes over the right side valve cover. Check to see if it is burned through at all. Found this in a buddy's 93 Astro after a no start and ECM fuses kept blowing.

I got it going!!! purring like a kitten. not sure how... or why :-k

after physically swapping the AC and fuel pump relay resulted in nothing but some relay clicking. then pulling out the ecm and whacking it a few times again resulting in nothing.

i was repeatedly turning the key on and off and trying to get some codes after jumping the A and B on the diag port. nothing. not even the 1 - 2 flashing. i was just about to give up for the night and noticed some wasps travelling to and from their home behind the mirror glass on the drivers side. i proceeded to kill them one by one with my ball cap and get the nest out. then i went back to wiggling the relays and turning the key and i gets a click click hummmmm i crank it and it fires up.. roughly but it fires.. i kept my foot on the gas to keep the rpms up so it wouldn't die.. and it would sputter every few seconds, as the sputter would happen the check engine light would light up .. when it wasn't sputtering the light was out. this lasted about 2 - 4min... then it quit sputtering.. i goosed it a few times and was able to let it idle on it's own without sputter or dying.

once i was sure that it was running ok i hauled ass back to my place with the van and let it run at least another 1/2 hr with no troubles at all. even going so far as to shut it off and start it again a few min later with no trouble. then 40min later tried it again with no trouble and smooth running.

i was then able to jump the A and B and get 1 - 2 flashing with NO other codes...

i'm really really realllllllly at a loss. yet, i'm afraid to drive the thing... LOL

seems after two days of smooth running (in the driveway) and only the odd stall or two I may have found the problem.

the main wiring harness that passes the huge clump of wires through the passenger side footwell right in front of where the doghouse meets the firewall. this massive mess of pretty colors is in a loom housing that is laying right across the passenger side valve cover. as soon as i press on the wiring or lift it the van will stall/quit

so, here's my question... I'll ask simply because there's hardly any length to get the harness to a easy viewing area, knowing what I'm looking for before I start would be helpful

what colors am i most concerned with checking?

fuel pump, fuel pump relay, any others? etc?

What I did to repair my friends' van was to pull the split loom off and split each wire from the bundle. I then inspected each one individually and any I found to be in question I cut, slipped heat shrink tubing around and soldered back together. We then taped the bundle and placed a heat resistant material (I forget what it was but it was a fiber board material) between the wires and valve cover and ty-rapped up out of the way as best we could.

thanks ... there's like 100 wires in that main bundle .. eeww i'm not looking forward to it.. LOL

well.. i had it running and started to unwrap the loom from the large harness and it died.

it started pouring rain here tonight so i'm going in blind tomorrow morning, first thing. hopefully I can track it down to which is shorting out or losing the connection. now that the loom is off i can't get the pump to engage at all

Just take a chill pill when you start to check the wires. It's really not as bad as it looks once you get going. Just time consuming. Check for obvious broken wires. If nothing is found try and stretch them. If the wire is broke inside the sheathing it will stretch. I found that out tracking broken wires between the doors and body.