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Fuel pump cuts out even after replacement

Old 06-08-2012, 01:25 PM
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Fuel pump cuts out even after replacement

Vehicle is a 1999 Camaro that my buddy has. We just replaced the fuel pump and it's still randomly cutting out. When it cuts out, you have to wait 5-15 minutes for it to start back up. There's zero fuel pressure at the shrader valve. His stupid mechanic told him he bought a defective fuel pump but I didn't believe it. Since my friend got the pump online to save $200 over the mechanic's price on it, he won't warranty the pump.... but I know it's not the problem. I put the old fuel pump in a bucket of water hooked it up to a 12v battery in my garage and ran for 2 days straight without shutting off (come to think of it, it made me want to make a fountain out of it ) So even the original fuel pump wasn't defective.

He already replaced the relay with a new one. Could it be the computer or is there some other relay/switch/controller that it could be?

He's already $600 deep in diagnosis and replacement and I told him I'd ask on here. My original idea was to just run a completely different wire to it on an ignition-on controlled relay with an emergency kill switch under the dash. So like a radio if you turn the key, the fuel pump comes on. In the event you want to kill the fuel pump for whatever reason, just flip the switch as a backup. Not sure if this will work if the computer needs to know when the fuel pump is on or even if it controls it for a reason.

The best idea would be to fix the issue at hand, but he's ready to sell the car as is because he's so frustrated and broke. That's where I'm stepping in to help.

Thanks guys!
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Old 06-09-2012, 09:36 AM
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Re: Fuel pump cuts out even after replacement

Has he replaced the fuel relay that is behind the kick panel on the drivers side? Have him check that relay in addition to the one that is underneath the hood in that fuse block.

Also, the racetronix kit is a seriously better pump for the money. Get the harness as well, definitely worth it in the long run.
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Old 06-09-2012, 09:48 AM
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Re: Fuel pump cuts out even after replacement

I don't think there is a quick answer for something like this. There is a really good diagnostic flow chart in the service manual for these sort of things. They basically go section by section through the wiring. You need a fuel pressure gauge and scan tool - the scan tool can command the pump on and off.

A couple of things to check when it quits:
- If you just turn the key on without starting it, the pump should run for a couple seconds. You can use this in place of a scan tool for some tests. Key the car on and see if it runs for a couple seconds or stays running.
- Unplug the relay, and use a test light to determine if power is going to the relay when you key it on. Use this techique section by section through the wiring to see if there is a wiring problem.
- Last on the list is replace PCM. If you know someone with an identical car, you can probably swap it.
- Fuel pump relay is one of the last things they swap, so I would focus on a corroded connection, bent pins, broken wire, etc.

-Geoff
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Old 06-09-2012, 10:19 AM
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Re: Fuel pump cuts out even after replacement

Thanks guys. I'll have him troubleshoot some more. I have a cheapy scan tool but not sure if my $70 one can turn the fuel pump on and off. As for the manual you're referring to a chilton's manual or similar correct? I'll have him pick one up and see what it says. I'll report back next week with our findings.
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Old 06-10-2012, 08:37 AM
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Re: Fuel pump cuts out even after replacement

Originally Posted by 96WhiteZ28 View Post
Thanks guys. I'll have him troubleshoot some more. I have a cheapy scan tool but not sure if my $70 one can turn the fuel pump on and off. As for the manual you're referring to a chilton's manual or similar correct? I'll have him pick one up and see what it says. I'll report back next week with our findings.
GM Service Manual.

-Geoff
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Old 06-12-2012, 09:01 AM
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Re: Fuel pump cuts out even after replacement

Check ground 305. It's located in the middle of the drivers side rocker panel near the driver's seat. I've seen a couple cars break that ground, and one broke all but 2 wire strands that would overheat within a few minutes of operation killing the pump.
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