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Discussion Starter · #1 ·
I installed a Holley fuel pressure gauge on my Holley fuel line and the needle bounces constantly but consistantly. The only time it is steady is at hi RPM's. Is this right?

Also, what should the fuel pressure reading be at idle and at hi RPM? I have a 350 with a stock fuel pump.
 

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I installed a Holley fuel pressure gauge on my Holley fuel line and the needle bounces constantly but consistantly. The only time it is steady is at hi RPM's. Is this right?

Also, what should the fuel pressure reading be at idle and at hi RPM? I have a 350 with a stock fuel pump.

Yeah, the bounce is normal for any pump running that slow. Only an oil dampened gauge will stop the bounce but they're expensive. And the pressure should remain at about 5 psi during all operating conditions. But to truly know what your pressure is under a full load you'll have to run a hose into the cabin like I recently had to do.
 

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Discussion Starter · #4 ·
it bounces with the pulses of a mechanical pump..5-6 psi at idle
Thanks, thats what I get at idle.

Yeah, the bounce is normal for any pump running that slow. Only an oil dampened gauge will stop the bounce but they're expensive. And the pressure should remain at about 5 psi during all operating conditions. But to truly know what your pressure is under a full load you'll have to run a hose into the cabin like I recently had to do.
Understood. BTW, I get 8 lbs while holding at 3k RPM.
 

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my gauge is on the regulator itself and still bounces slightly.. I too had 8psi at 3000 rpm from my Holley mech pump.., when I hit WOT, and then let off, it would flood .. regulator prevents that...I set mine at 5.5 psi, and that feeds my stroker just fine
 

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Buster, to stop the gauge flutter you can buy a gauge snubber, it will take out the pulsations of the pump. I think they are about 9 dollars from McMaster-Carr. I used one on my oil pressure gauge because I had a small hole drilled in the the idler gear to lube the shaft and every revolution of the oil pump I would get a slight drop in pressure. A gauge snubber cured the problem. :seeya:
 

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I,m ordering a fuel pressure gauge for my fuel injected lt-1. Can i expect the same bounce or flutter with fuel injection? should i expect the same readings?
No, your pump (electric) is a centrifugal or turbine type pump and not as prone to pulsation like the diaphragm pump. The diaphragm pump works by cycling(one stroke up and one stroke down) a diaphragm, but it only builds pressure on one of the strokes, not both. Thats where the pulsation comes in, on the stroke where there is no pumping action. So you get pumping action on every other stroke, hence the pulsations.
 

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Discussion Starter · #14 ·
No, your pump (electric) is a centrifugal or turbine type pump and not as prone to pulsation like the diaphragm pump. The diaphragm pump works by cycling(one stroke up and one stroke down) a diaphragm, but it only builds pressure on one of the strokes, not both. Thats where the pulsation comes in, on the stroke where there is no pumping action. So you get pumping action on every other stroke, hence the pulsations.
one other itemvyou may want to consider. I have learned in my research that the oil filled gauges can change pressure reading as a result of underhood heat.:backstabber:
 

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one other itemvyou may want to consider. I have learned in my research that the oil filled gauges can change pressure reading as a result of underhood heat.:backstabber:
Yes I quess it's possible, if the glycerin in the gauge body builds pressure, but usually the seal for them is not that tight, so it will bleed off pressure. And you will usually see a bubble inside the gauge body when that happens. :catfight:
 

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Discussion Starter · #17 ·
Yes I quess it's possible, if the glycerin in the gauge body builds pressure, but usually the seal for them is not that tight, so it will bleed off pressure. And you will usually see a bubble inside the gauge body when that happens. :catfight:
that info was in the explaination portion of the summit racing part description for the oil filled ones. Putting it in the cab wood do it tho.
 

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that info was in the explaination portion of the summit racing part description for the oil filled ones. Putting it in the cab wood do it tho.
A fuel gauge in the cab or vehicle's interior is not recommended unless a fuel isolator is used. You don't want fuel pouring into the cab if a leak were to develope.:toilet:
 

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A fuel gauge in the cab or vehicle's interior is not recommended unless a fuel isolator is used. You don't want fuel pouring into the cab if a leak were to develope.:toilet:

If I were going to install a fuel pressure gauge inside my cabin I would ONLY use an electric gauge. But for testing purposes I have no problem using the same 1/4" diameter 300# hose I use for reading transmission pressures.
 

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Discussion Starter · #20 ·
A fuel gauge in the cab or vehicle's interior is not recommended unless a fuel isolator is used. You don't want fuel pouring into the cab if a leak were to develope.:toilet:
good point. for the record, i was not advocated that, only commenting on the gauge reading re temperature to accuracy.
 
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