C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Fuel pressure problem

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Old Jun 3, 2013 | 08:24 AM
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Default Fuel pressure problem

I installed a fuel pressure cauge and pressure is around 39-36psi.
My problem is that the pressure drops suddenly to 15-20psi when I drive the car. Of course car drives horrible.
I have changed the fuel filter, no help.
When the pressure is ok and I turn off the engine, pressure stays up for many hours.
What can I test next? I heard about dynamic fuel pressure test but I haven't found out how to do it.
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Old Jun 3, 2013 | 03:25 PM
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I would take a look at the fuel sock in the tank and the hose running from the pump to the steel line, also in the tank.
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Old Jun 3, 2013 | 03:43 PM
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Time to replace the fuel pump and sock. It is very easy on the Corvette. And buy the Made in USA Weber. The Edelbrock unit uses a Weber pump.
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Old Jun 3, 2013 | 03:48 PM
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Originally Posted by mixalive
Time to replace the fuel pump and sock. It is very easy on the Corvette. And buy the Made in USA Weber. The Edelbrock unit uses a Weber pump.
Where can I buy such unit?
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Old Jun 4, 2013 | 01:41 AM
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all you need is a new pump. They come with a strainer.

if you want a good one, the racetronix is a very popular upgrade.

These pumps wear out because everyone insist on driving hard with less than 1/2 tank of gas. Can't do that. The pump is cooled by being submerged in gas and the first time the pump sucks air it damages the rubber impeller. They do not like to be run hot or dry...

Half of what is found in fuel filters WAS/IS part of the pump as it disintegrates and sends chunks to the injectors.
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Old Jun 4, 2013 | 11:09 AM
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Edelbrock sells the same pump as Racetronics. Summit Racing, Jegs and even Advance sells it online.
Summit also sells the Granatelli GRN-GM722-2 for $125. It is probably a Weber as well. The cheapy $69 pumps are probably not Weber.

Last edited by mixalive; Jun 5, 2013 at 09:37 AM.
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Old Jun 10, 2013 | 04:39 PM
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Thanks to everyone. Another question. I measure about 12.6 volts from the fuel pump wiring harness when the car is running. At the same time I can read 13.7 volts from the battery. Is this voltage drop normal and will the fuel pump run correctly with 12.6 volts?
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Old Jun 10, 2013 | 04:52 PM
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Originally Posted by vtormane
Where can I buy such unit?
Racetronix. I'd get it but not the other harness to run power from the alternator unless you have a power issue.
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Old Jun 10, 2013 | 04:55 PM
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Originally Posted by leesvet
These pumps wear out because everyone insist on driving hard with less than 1/2 tank of gas. Can't do that. The pump is cooled by being submerged in gas and the first time the pump sucks air it damages the rubber impeller.

They do not like to be run hot or dry...
I think that is an old wives tale. At that rate, I'd be changing my pump every week. My car runs down to the bottom then gets filled up.

If it needs that much cooling, it would be a fire hazard. As long as fuel flows thru it, it is cooled. Now if fuel stops, the engine cuts out and the pump stops so no heating
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Old Jun 12, 2013 | 05:07 PM
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voltage drop normal. That pump will run on 9 volts. Don't worry about the incidentals.
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