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post #1 of 9 (permalink) Old 11-23-2012, 07:01 PM Thread Starter
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Fuel issue on 94 vette

Knowns: Fuel pump and strainer 1 1/2 years old, fuel filter less than a month old, fuel pressure regulator is the 2nd one installed in the last 30 days.
With KOEO fuel pressure is 37psi (measured with two different FP gauges) and it take from 10 to 12 minutes to bleed down from 37 psi to 30psi.
Have no idea if this is within specs or not? With engine running (which is not often) fuel pressure is 37psi. Due to car dying at will, have not tried getting it out on the road. Car does not run
rough and or miss when it can be started? Sure would like to get the car up and running.. Any thoughts or suggestions..
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post #2 of 9 (permalink) Old 11-23-2012, 07:44 PM
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You are not helping yourself by starting more threads on the same no start problem.
Do you now have good steady ign spark and timing?
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post #3 of 9 (permalink) Old 11-23-2012, 10:02 PM
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Quote:
Originally Posted by Anthony Dale Enloe View Post
With KOEO fuel pressure is 37psi
Have no idea if this is within specs or not? .
Don't think it is your problem but pressure should be higher
Fuel pressure on LT1 without the vacuum line connected should be 43.5psi @ idle (or KOEO )
Should drop about 6-8 PSI @ idle with the vacuum line connected.

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post #4 of 9 (permalink) Old 11-24-2012, 05:37 AM
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Quote:
Originally Posted by Anthony Dale Enloe View Post
Knowns: Fuel pump and strainer 1 1/2 years old, fuel filter less than a month old, fuel pressure regulator is the 2nd one installed in the last 30 days.
With KOEO fuel pressure is 37psi (measured with two different FP gauges) and it take from 10 to 12 minutes to bleed down from 37 psi to 30psi.
Have no idea if this is within specs or not? With engine running (which is not often) fuel pressure is 37psi. Due to car dying at will, have not tried getting it out on the road. Car does not run
rough and or miss when it can be started? Sure would like to get the car up and running.. Any thoughts or suggestions..

It's very possible your fuel pump relay is failing and that's why it won't stay running. I suggest using a trickle charger to power your pump and then see if it dies. Just disconnect the wires at the fuel tank then supply power directly to the fuel pump's hot wire. If it doesn't die then you can assume the relay is failing or power to the relay is getting interrupted (the power comes from the oil pressure sender). Over time the points in the relay get a carbon buildup and they'll work until they warm up then suddenly quit. If your car has anywhere near 100,000 miles I suggest simply replacing the relay so you'll know it's good and will stay good for a long time...................

Last edited by toobroketoretire; 11-24-2012 at 05:44 AM.
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post #5 of 9 (permalink) Old 11-24-2012, 02:32 PM
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Originally Posted by toobroketoretire View Post
I suggest using a trickle charger to power your pump and then see if it dies. .
There is a fuel pump prime connector under the hood that allows you to put 12V direct from the batt to the pump bypassing the relay

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post #6 of 9 (permalink) Old 11-25-2012, 10:35 AM
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Originally Posted by vetteoz View Post
There is a fuel pump prime connector under the hood that allows you to put 12V direct from the batt to the pump bypassing the relay

That's good to know. The object of powering the fuel pump from another source is to eliminate the possibility of the relay or a bad connection at the oil pressure switch causing the engine dying. Just a part of the troubleshooting process.

The fuel pump gets it's power from the battery but it gets energized by two sources; the ECM for 2 seconds and the oil pressure switch. As long as there is at least 5 psi of oil pressure the relay should stay energized.
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post #7 of 9 (permalink) Old 11-25-2012, 12:23 PM
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He has a fuel pressure gauge which would immediately show if the pump was not being powered. As far as I am concerned, he has an ign problem unless he states that he has good spark and correct timing, and if he states that then it will be time to address the fuel system........... Read his original no start/run thread. Note that nowhere does he say that he actually checked for spark and correct timing, and whether or not he has it: 94 coup with AT left me on the side of the road again!!!

Last edited by Slicktop; 11-25-2012 at 12:29 PM.
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post #8 of 9 (permalink) Old 11-26-2012, 02:30 AM
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Originally Posted by toobroketoretire View Post
As long as there is at least 5 psi of oil pressure the relay should stay energized.
OP switch doesn't power the relay ;
it supplies power direct to the pump as a backup should the relay fail allowing you to start and run the engine as soon as OP comes up while cranking



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post #9 of 9 (permalink) Old 11-26-2012, 07:36 AM
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Quote:
Originally Posted by vetteoz View Post
OP switch doesn't power the relay ;
it supplies power direct to the pump as a backup should the relay fail allowing you to start and run the engine as soon as OP comes up while cranking


Do not worry about it, Toobroke does not know anything about c4 systems and has never owned one.
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