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Lee Lee is offline
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fuel pump relay question

I checked a bunch of vapor lock threads, but didn't find one that matched my circustances.

I own a 78' SC, with CIS. I'm experiencing what seems to be vapor lock...starts up fine when cold...doesn't start when hot, but turns over. However, I tried to push up slightly on the sensor plate, with the inginition on, and while I felt definite resistance (which would seem to indicate fuel pressure), the injectors didn't sing, and no fuel was forthcoming.
So I push started it, and it pretty much started right up.

It doesn't always have the hot start problem. I haven't done a pressure test, yet...waiting for tester...probably this week-end.

I'm wondering if itcould be the relay, and can I safely check it out by temporarily swapping it for one of the other relays to see if it starts?

Thanks for any input.

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Daniel Crockett
'78 SC Targa
Old 10-17-2005, 08:11 PM
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Do you have a red relay in the fuel pump relay socket now?
Old 10-17-2005, 08:21 PM
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Lee Lee is offline
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Yes.
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Daniel Crockett
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Old 10-17-2005, 08:31 PM
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You check for a damage WUR?
With the engine hot, take a rag, wet it with cold water, put over the Warm Up Regulator, wait a few minutes, add cold water over the rag, slowly, then try to start the engine. If the engine starts and run, you have a bad WUR.
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Are you car loosing power? When was last time you service your fuel injectors? Dirty fuel injectors? Why no try a complete fuel injector cleaning service and return the dignity to you car. Visit www.rennsportfuel.com and we will return your injectors back to life!
Old 10-17-2005, 08:49 PM
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If you do a search regarding red and black relays, it appears fine to substitute a black relay for a red one for testing purposes. I would use a horn relay since it is easy to test and make sure it is working properly. For that matter, I guess you can swap the two relays and see if your horn works with the fuel pump relay installed.
Old 10-17-2005, 08:59 PM
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You can find lots of help by doing a hot start problem search. Some other likely candidates are the fuel pump check valve and the fuel accumulator. Have you checked the cap, rotor and wires?
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Old 10-17-2005, 09:14 PM
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Cool start - no start.....

Lee,

Check to see if you have a marginal battery. If the starter is pulling too much of the available power from the battery, then the fuel pump could be under powered and not providing enough fuel pressure. Take your car to an auto parts store and let them put a load tester on the battery to check for a weak cell.

Good luck!
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Old 10-18-2005, 04:18 AM
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Lee Lee is offline
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Thanks for all the answers...

I checked the battery, it's okay. The cap and rotor are pretty new, but I checked them, and they seem okay...

I hadn't thought of substituting the fuel relay for the horn, good idea. And I've never heard of the rag trick, but I've been wondering how to test it, so I'll give it a try today. I have an extra WUR hanging around, if needed...it looks easy to swap out.

My car's been down since July. I dropped the engine, replaced the exhaust studs, parts of the exhaust system, pulley seal, gaskets and seals on the CIS, intake sleeves, oil pressure sensor, oil pressure sender, and a few other little things I can't recall. Before that, I had a horrible vacuum leak and exhaust leak backfire. I don't remember a hot start problem, before all that.

I should be getting a pressure tester in the mail any day...wishing I had a fuel/air mixture tester.

thanks

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Daniel Crockett
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Old 10-18-2005, 05:15 AM
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