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Old 12-01-2010, 12:08 AM
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Default Help with Fuel Pressure Gauge Readings

I have a non-dampened fuel pressure gauge mounted where I can watch it while driving, the readings are very erratic.

I've had to change the fuel pressure regulator due to it fluctuating while the car is sitting there idling. This is the second Holley large port regulator that I have used and I'm starting to question if this one is working correctly.

I've herd this regulator fluctuating while idling and I could see it on the gauge also.

If anyone out there has a non-dampened fuel pressure gauge mounted where you can see it while driving does it swing wildly?

Mine swings from 0 to 15 psi sometimes and at other times it stays fairly smooth.

I'm starting to think it may be the internal pressure relief spring in the pump.

Or possibly the pump relief is fighting the regulator

I did have the return line connected but disconnected it for a while but now it is connected again. I have noticed that the fuel pressure fluctuating issue is better with the return line connected but it still does it.

Just can't imagine that I got two bad Holley regulators in a row.

Neal
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Old 12-01-2010, 02:02 PM
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I think you'll find some regulators are set up for a return line and some aren't. If you're fuel pump is set up for a return line, you have to have it connected, as I understand it, the internal bypass is different for a return/non-return pumps. I'd bet if you give the Holley folks a call, they'll tell you how to set up your regulator. You may even need a different type of regulator.
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Old 12-02-2010, 11:46 PM
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My son installed his on the Schrader valve - with the Schrader valve removed - and the gauge taped to the windshield.

Readable and no fluctuation of the reading.

Jake
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Old 12-03-2010, 02:35 PM
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496BBC 496BBC is offline
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Thanks for the reply Jake,

been wondering if others were seeing the fluctuations or if the gauge should be steady.

I've sent Holley an email with the part numbers of the parts I'm using to see if maybe I have miss matched them or if something else may be wrong.

Neal
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Old 12-04-2010, 07:03 AM
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Originally Posted by 496BBC View Post
Thanks for the reply Jake,

been wondering if others were seeing the fluctuations or if the gauge should be steady.

I've sent Holley an email with the part numbers of the parts I'm using to see if maybe I have miss matched them or if something else may be wrong.

Neal
My 90 vette f/p fluctuates too, this is the first TPI I have seen do this. I'm wondering if I have a blocked return line or the pump is pushing air at times.
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Old 12-04-2010, 12:28 PM
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Ryan used a FP gauge (with the long hose) taped to the windshield when he was setting up his new AeroMotive adjustable fuel pressure regulator.

Are you guys mounting the gauge to the Schrader valve location with the valve removed?

Jake
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Old 12-04-2010, 12:48 PM
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Mines mounted to the fuel log at the carb, no schrader valve


Neal
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Old 12-04-2010, 01:37 PM
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Quote:
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Quote:
Originally Posted by 496BBC View Post
Thanks for the reply Jake,

been wondering if others were seeing the fluctuations or if the gauge should be steady.

I've sent Holley an email with the part numbers of the parts I'm using to see if maybe I have miss matched them or if something else may be wrong.

Neal
My 90 vette f/p fluctuates too, this is the first TPI I have seen do this. I'm wondering if I have a blocked return line or the pump is pushing air at times.
That TPI is batch fire, same as mine.....I noticed some odd symptoms about it over the years....it has had some operational problems, but not fuel pressure related, which is why I went through all that in the first place to even notice this....

I was using the lo side of my a/c gauges for fuel pressure readings did fine....then the hose failed, and I decided to put a old oil pressure gauge on a copper line into the setup....so hooking that up I saw all sorts of fluctuations not apparent in the a/c gauge, with engine operating....it's the obvious fuel pressure variations due to batch firing 4 injectors at once....

another thing I noticed, was that Erol's fuel line I was using, was a really good rubber line, never leaked once, BUT strangely enough, if I grabbed it with engine running I could feel the pulses in the rubber line....later on, after switching to the LT1 induction, I noted the lines were really pulsing, and so subbed in some Aeroquip steel mesh with black cloth over it, same as I used on a boat years ago, and upgraded the clamps too, just for shits and giggles....the pulsing went away from the lines, and so I have left it alone at this point, the gauge evened out too....go figger....
engine seemed to smooth out a bit,
but with this ethanol crap, I still get some erratic operation....
but not nearly as bad as before....

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