Hi all, I created a new account as deekstercaddy bc I was unable to recover my old account (formerly deekster_caddy), so I'm skipping the 'introductions'. '04 GP GT with a big problem. Intermittently the fuel pump stops running, sometimes at start, sometimes while driving (!). It may be a few days between failures, may be a few hours, may be a few weeks. It seems to be more pronounced now that it's hot. I'll give a rundown of all the troubleshooting we have done.
1) found that the pigtail at the fuel pump itself was loose, and the pump very noisy. Replaced pump, replaced wiring pigtail (the plug and wires came with the new pump!). At the time I thought it would be neat for testing, so I wired a 194 bulb socket to the fuel pump wire and fed it up into the trunk. Turns out this is the best thing since sliced bread, because the problem was not solved and it's really nice to have an indicator light as to whether power is getting back to the pump. The fuel pump is a lot quieter now at least.
2) when the car dies, we know the fuel pump isn't running because the light doesn't come on. Light on = fuel pump on. No light = no fuel. When we are having issues I slide the light through the back seat so we can see it from inside the car.
3) when the fuel pump won't turn on, wiggling or removing and reinstalling the FP relay under the hood "fixes" the problem for a while. We tried swapping with other relays in the box and the problem is the same - intermittent and somewhat unpredictable. Wiggling/removing the relay fixes it.
4) I thought the relay was pretty loose in it's socket, so initially I messed around with bending pins on the relay trying to make a better contact. I then tried building the pins thicker with a little solder, twisting the pins etc - a couple different things. Finally I called up Morads and got a replacement for the entire underhood fuse box. I used a different relay (not the one I bent pins and built up with solder) and the relay fits tightly now, but our problem is the same. Wiggling/removing the relay fixes it.
5) Tried swapping a bunch of different (old) relays. Finally I bought a brand new relay. Still fits nice and tight in the fusebox. Problem is the same.
6) Took out the fuse box and checked wiring harnesses with an ohmmeter. Wiggled and pulled wire harnesses all directions, unable to cause a failure. I was hoping to find a broken/brittle wire to replace. I disassembled the large plug on the back of the fusebox and wiggled and pulled the individual wires on this relay. The trigger from the ECU (green wire w white stripe I think) is good, feed to the pump (grey wire w red stripe I think?) is good. Also loose or brittle wires don't explain to me why wiggling the relay is the fix. I'm not moving any wires when I do that.
7) swapped PCMs, reflashed w old PCM program and VIN. Problem is the same. Wiggling the relay fixes it.
What am I missing here? I've tested and replaced every part I can think of. I suppose I could try replacing wiring harnesses completely, but this really, really doesn't seem like the issue, nor does it explain why wiggling the relay makes it work again.
Any advice?
Thanks!
-Derek
Originally Posted by The Sunfire Guy
