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Discussion Starter · #1 ·
I installed a fuel pressure gauge inline because Edlebrock advised the stock BB pumps pressure of 8 PSI was too much. They said it should be no more than 6 - 7 psi. I noticed the gauge would quickly return to zero once the engine was shut off. Where does the pressure bleed off to?
 

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I would think that it bleeds off back where it came from. I don't think you have a problem.
 

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i would think because the pump isn't creating the pressure it would drop of i dont thing theres a problem there either…
 

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I dunno guys, i have a stock mechanical pump, and after shutting down the engine, if I loosen up a fuel line gas comes out under pressure. Not LOTS of pressure mind you, but it is being forced out, not just running out.


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thats a mechanical pump in the even that its an electric would that make a difference? if not is it possible that the guage is an electric guage or its somehow wired to the ignition?

Where is this guy hes got alot of questions to fes to
 
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Discussion Starter · #7 ·
The pump is mechanical and the gauge is just an inline mechanical regulator. No wires attached to it. I was just curious if the gas was bleeding into the carb, the engine or back to the pump and tank.
 

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Most pumps I've checked over the years usually tend to bleed down in around ten to fifteen seconds. That's not to say your pump is bad. If it holds a steady pressure while running and the gauge needle does not oscillate, I wouldn't worry about it.
 

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In a noncompressible fluid (such as gas), once the pump stops functioning, there is theoretically no pressure. The only thing holding residual pressure would be the rubber lines that have expanded under pressure, and this small amount would quickly bleed back. Once the lines are back to normal (unstretched) size, even though full, the pressure would be 0.

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Ledsled: What about the rubber diaphragm in the pump, getting pushed down by the spring? There's your 6-8 PSI, and a bit of volume, too.

I say the fuel pump check valve (s) is bad, and the pump is draining fuel back to the tank.

Stock type mechanical fuel pumps are about as cheap as dirt, try a new one.
 

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Next thing you know someone will be posting "why does my oil pressure gauge go to zero when I shut off my engine?" j/k, relax, everything is o.k.

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Right now I've got a gauge on my fuel line and it stays at 6 psi for up to an hour after the engine is off and then slowly bleeds down to 0 over the next couple of hours.
 

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I love it when someone asks a question but does not state that there is any problem whatsoever with the car. By John own words, it pumps 8 psi while running, and he is regulating that down 1 to 2 psi per Edelbrock's recommendation.

If your car runs fine you can still replace parts as you please, but if it is running fine then why would you want to spend money and time unless there was a problem?

So relax when your fuel pressure and oil pressure go to zero when you shut off the engine. Worry if your oil and fuel pressure do not come back when you restart the engine.
 
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