Blowing Fuel Pump relay

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Re: Blowing Fuel Pump relay

Postby lumbercis » Sat Nov 19, 2016 9:20 pm

So kind of an interesting report from the shop guys.

They replaced the fuel pump and buttoned everything up. The car starts and runs but they are saying that the relay is still running slightly hotter than normal. Not as bad as before where it was getting very hot to the touch and then blowing within a minute or two. They pulled out this tool that's basically a little infrared scanner that they point at the relay that lets you see the internal heat being produced so while the relay wasn't super hot to the touch, it was definitely showing up brighter than any of the other relays on the infrared scanner.

The mechanic basically said that while the car starts and drives he can't guarantee how long the relay will last. I asked them specifically whether they checked all the wiring, grounds, and any associated parts like the fuel filter and they said everything checked out. Although tbh I'm pretty sure they must be missing an electrical problem somewhere.

Random question: I noticed my tach adapter (MSD 8910 or 8920 I think) has been going out (losing the tach signal) more often around the time this relay problem started. Just coincidence or should I investigate more? I can't think of how the tach adapter would affect anything but maybe they both have the same root cause somewhere?

Anyway, I think I'm going to go pick up the car from these guys and maybe take it to a speed shop that's more comfortable dealing with modified cars and see if they can find the problem.
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Re: Blowing Fuel Pump relay

Postby alltracman78 » Sun Nov 20, 2016 4:26 pm

I hope you kept the other pump. All you need is someone that knows how to troubleshoot electrical problems they don't have to know modified cars at all. Your MSD adapter might have something to do with it. it depends where it's wired in. which circuit it is using.
it sounds to me like the relay is burning up on the coil side. if that is the case the pump has nothing to do with it. It's also possible you have a loose connection where the relay plugs into the fuse box.
you know what you could have done comma removed the relay and put a fuse in its place. if the fuse blew that would tell you if the pump side if not it would be the coil side.
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