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post #1 of 26 (permalink) Old 06-27-2016, 09:30 AM Thread Starter
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high fuel pressure

Just installed a Racetronix 255 fuel pump and harness because my old pump was not keeping up at WOT, changed fuel filter as well. The problem I am having is my fuel pressure reads 51psi at prime, 50 to 51 at idle, and when I disconnect the vacuum to regulator the pressure goes up to 54psi, then when I shut the engine off, I loose all pressure in a few minutes. Before I did the swap fuel pressure never dropped off. Could this be the regulator?
Any suggestion would be great.

95 Trans Am Lt1, LE1 head, custom cam, 30# injectors
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post #2 of 26 (permalink) Old 06-27-2016, 10:29 AM Thread Starter
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update,
just blocked off the return line and done a prime, fuel pressure went up over 100, and still dropped off, maybe its my cheap fuel gauge? According to my data logs the car is running rich, low blms 104 106 in cell 4, the other cells is not so bad 113-114, 118-119, I also noticed in my log high o2 reading when high, just replaced o2 sensor with AC/delco. Car has a Solomon tune, hes the one who told my the car is starving for fuel at WOT, that's why I changed the pump.

Any suggestion would be great. Maybe I missed up pump connections? Gotta trap door cut.
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post #3 of 26 (permalink) Old 06-27-2016, 12:23 PM
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Your regulator may not be opening enough to bring pressure to normal 43 psi at key on prime and around 36 psi when idling.

Increased fuel pressure means that more fuel is added then needed. Your pcm is calculating amount of fuel to spray using 35-43 psi as it's basis.

When fuel pressure falls quickly after shut down, there are several things that can cause this. Check ball in pump may be defective. regulator stuck open a little bit. Or fuel injector/injectors stuck open. Finally, leak at where fuel hose attached to fuel pump.

Since pump only has positive & negative wires to hook up, don't know if that is your problem. If you hooked pump up backwards, It would run backwards. I've never tested the output of a fuel pump running backwards to know what effect it would have on fuel pressure.

But my guess is, it would pump fuel away from fuel rail back to tank, if pump leads reversed.

Last edited by cocobolo95; 06-27-2016 at 12:29 PM.
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post #4 of 26 (permalink) Old 06-27-2016, 12:48 PM Thread Starter
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I just took out the pump again, all the hoses are hooked up right, pump as about 50km on it, hope its not check ball in pump, I fitted a old 96 Corvette regulator on my fuel rail just for test and had the same results. I order a new regulator but it won't arrive for another 10 days. Yesterday morning I done a pressure test before the new pump install, I had 42 psi on prime and it stayed pressurised, only thing I never checked when I removed the pump was positive and negative feed to pump. Guess its out with the pump again.
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post #5 of 26 (permalink) Old 06-27-2016, 12:50 PM Thread Starter
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One more thing, engine runs good, if I never had my laptop plugged in, I would never no there was a problem except for hard starting due to fuel pressure bleeding off.
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post #6 of 26 (permalink) Old 06-27-2016, 01:10 PM
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with your raceTronix kit it may be necessary to run a adjustable FPR to set the FP where it needs to be

your rich readings and high 02 counts are because your FP is to high. The PCM can not compensate for it that high

you can buy a adjustable FPR at some auto part stores. I got mine at Advanced Auto. BWD (borg warner) # 23065. direct fit
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post #7 of 26 (permalink) Old 06-27-2016, 02:11 PM Thread Starter
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I only got the 255LPH pump and harness, says stock replacement, did not read anywhere when ordering that pump that I needed a adjustable regulator. Did your pump do the same with stock regulator, high pressure and bleed off quick. Kinda like to no for sure before I order more parts.Pretty much got my car budget used up for this year lol.
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post #8 of 26 (permalink) Old 06-27-2016, 02:33 PM
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I don't have a RaceTronix kit. I do have a Walbro 255 pump though which does put out more than the stock pump but I didn't have high FP with a stock FPR as a result. The pressure does bleed off in about 10 min once I shut down

For whatever reason your stock FPR is not stabilizing the pressure.

I can't remember how much $ my adjustable was, IIRC around $55. I bought it when my original FPR started leaking fuel into the rubber vac line. $ for Delphi, AC Delco, etc are around $40-$80 for a standard replacement FPR on rockauto.com

IMHO stay away from Aeromotive

While my tune is based on stock FP, I use the adjuster screw to put it dead nuts there. If you turn the pressure up you can see the 02 readings start to read high and ST & LT fuel trims change so to much pressure is going to negatively affect the car as PCM can't compensate for it. You will run rich as a result of to much FP
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post #9 of 26 (permalink) Old 06-27-2016, 02:44 PM Thread Starter
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My regulator is not leaking Not that I can tell. Guess I might as well order that adjustable one. The stock one I ordered is about 130$ Canadian Hopefully I can get my deposit back. Thanks for your input.
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post #10 of 26 (permalink) Old 06-27-2016, 04:01 PM
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your FP readings by your gauge is high and the data of the 02, etc are high so your Racetronix FP is faulty causing higher FP or your regulator is not adjusting it correctly.

You don't need a adjustable but for me it was the same $ range as a standard and is plug & play install as it is the same size/shape as stock one. It was available at 2 large chain auto part stores here (Advanced auto & o'rielys). IDK what you have in Canada....but the beer is better there :-)

Your in Canada...so I see why you went RaceTronix. Might want to contact their tech line and ask.
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post #11 of 26 (permalink) Old 06-27-2016, 08:19 PM Thread Starter
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Beer is pretty good here, I drink Canadian Budweiser, I think that's half my problem. I did email racetronix to see what they have to say. I will report back about customer service.
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post #12 of 26 (permalink) Old 06-28-2016, 11:35 AM
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Quote:
Originally Posted by Mdw95 View Post
. I will report back about customer service.
hopefully being Canadian will get you a reply...they don't have a good reputation on the customer service side/tech support. At least down here in the states.

I believe if you purchase something and then join their tech forum they answer ?'s
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post #13 of 26 (permalink) Old 06-28-2016, 11:48 AM Thread Starter
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I did get a reply from them after I joined there tech page, there saying that I got a return restriction. Never had one before, but I guess I will take the pump out for the forth time and check it out. Good job I when the trap door route.
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post #14 of 26 (permalink) Old 06-28-2016, 12:13 PM
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so they say the pump can't be returned?

did they say what FP unregulated it should put out?
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post #15 of 26 (permalink) Old 06-28-2016, 07:50 PM
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BallSS, you misunderstood. The company told Mdw95 there is a restriction in the return line to fuel tank.
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