My 454 Rebuild

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Spareparts

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I believe the FPR is bad. When I pinch off the return line pressure jumps to 80psi
 

Carlaisle

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Your fuel pressure is definitely far out of spec. It should be 58-62 at idle. There is a 44psi regulator that will physically fit. You were probably given the wrong one when you replaced it last year. The correct one for the L29 is FP10021.
 

454cid

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Bouncing between 40 and 45? That's low. I think mine was about 50 when I installed a new pump. How about using another gauge before pulling stuff apart.... unless you've already covered that, I admit I have not been closely following the thread.

My gauge is just a HF cheapy.... I did have to make a gasket so the fitting wouldn't leak.

When I pinched off the return line, my pressure jumped to 90psi before I knew it. I was a bit worried It would damage something, but thankfully nothing bad happened that I could tell.
 

Piratehunter

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good diagnosis technique. Glad you’re homing in on that miss. These threads are very helpful. I hacked one of my cheap fuel lines wrenches to get to those fuel line fittings a bit easier.
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Spareparts

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Here is the FPR i installed just now. Says it is 57psi
It now reads exactly the same thing for FP, 45psi But the needle is now steady and not fluctuating on the gauge like the old one.
So now is my new gauge reading wrong, or was the FPR packaged wrong?

I did not take the fuel rail off to change it. Just the upper intake, cap and rotor.
 

Carlaisle

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I would try a different pressure gauge. Oreilly probably has one you can borrow. If it reads the same you can be reasonably confident the problem is somewhere between the tank and regulator. I would replace the fuel filter if it has not already been replaced - it could be clogged. If pressure is unchanged with the new filter, it's time to drop the tank.
 

Spareparts

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The fuel filter was replaced last fall for no reason other than maintenance.
Yeah, im going back there in the morning and using their gauge and see what it reads
 

Spareparts

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Used a gauge at the parts store and it measured exactly the same thing. 2 FPR's gave the same PSI and two pressure gauges the same.
Even though the fuel pump will pressure up to a little over 80psi maybe it does not have enough volume to maintain fuel pressure?
 

Supercharged111

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Used a gauge at the parts store and it measured exactly the same thing. 2 FPR's gave the same PSI and two pressure gauges the same.
Even though the fuel pump will pressure up to a little over 80psi maybe it does not have enough volume to maintain fuel pressure?

If you question the fuel pump's volume, pin the gauge under your wiper and go for a quick rip to see if the pressure holds to WOT. If it does, regardless of what the pressure is, the pump is fine and your culprit is the regulator.
 

Spareparts

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FP gauge hose is to short for that and i can't get back to the parts store till tomorrow to hack a longer hose together, But.
I have verified the gauge reads correctly at 60psi. Adjusted my air compressor to 60psi and using a compression gauge it read 60psi then i hooked it to the FP gauge and it read 60psi so it should be reading correctly.
Till tomorrow maybe this will mean something.
Yesterday i pinched off the return line until the FP gauge read 60psi at idle and went for a drive fully warmed up with some heavy throttle.
Made 0 difference except 1.
The LTFT went from the usual +3.0 to -13.5%. STFT was normal +/- 0.5%
 
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