Chasing a leaking fuel pressure regulator problem
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Pro
Joined: Nov 2005
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From: North Bay Ontario
Chasing a leaking fuel pressure regulator problem
1985 L98
I've confirmed that I have a FPR that will not hold pressure after the 2 second prime of the fuel system. When I pinch the return line at the fuel tank, and prime the system, it primes to around 60 psi and holds steady. When I release the pinched line, the pressure will drop to about 5 psi in about 30 seconds and down to zero within a couple of minutes. Priming the system with the line unpinched - it hits about 42 psi and begins dropping off immediately. The car runs fine; however sometimes it will crank over for 5 or 6 seconds before firing up and other times it will fire right up as soon as I hit the key.
I installed a new FP diaphram with the stainless steel disc and when I had it apart, I inspected the seat in the FPR and it looked fine - no apparent pitting or corrosion. I even gently rubbed it with some fine emery paper just to clean it up. There is no difference between when I had the old FPR and the new one.
Has anyone dealt with this issue? Is my solution to replace the FRR base?
I've confirmed that I have a FPR that will not hold pressure after the 2 second prime of the fuel system. When I pinch the return line at the fuel tank, and prime the system, it primes to around 60 psi and holds steady. When I release the pinched line, the pressure will drop to about 5 psi in about 30 seconds and down to zero within a couple of minutes. Priming the system with the line unpinched - it hits about 42 psi and begins dropping off immediately. The car runs fine; however sometimes it will crank over for 5 or 6 seconds before firing up and other times it will fire right up as soon as I hit the key.
I installed a new FP diaphram with the stainless steel disc and when I had it apart, I inspected the seat in the FPR and it looked fine - no apparent pitting or corrosion. I even gently rubbed it with some fine emery paper just to clean it up. There is no difference between when I had the old FPR and the new one.
Has anyone dealt with this issue? Is my solution to replace the FRR base?
Instructor
Joined: Aug 2009
Posts: 146
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From: Broadway Virginia
You are not alone. See the thread: " Engine one side hot, one side cold...runs like crap" by My1st
In his case it comes and goes at random.
In his case it comes and goes at random.
Last edited by walter schweigert; Jul 11, 2010 at 11:07 PM.
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Joined: Nov 2005
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From: North Bay Ontario
Yeah - I've read the thread...although there has been a "chase" of a different nature, mine has always ran fine - it's just the occasional start up that takes longer than I like, and I'm confident that I've found out where the FP leak down is happening - just need to determine what to do about the leaking seal inside in the FPR.
Last edited by pletzvet; Jul 11, 2010 at 11:53 PM.
Race Director
Joined: Aug 2000
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Cruise-In II Veteran
You might have a bad check valve in the fuel pump.
My old 86 did the same thing and a new Fuel pump fixed it.
If you block off the return line and it holds,the FPR isnt leaking.Its the check valve in the pump.
One more thing to check,but usually isnt the cause,the cold start injector,if leaking,can cause a pressure drop.But Im betting my money on the check valve inside the pump.
My old 86 did the same thing and a new Fuel pump fixed it.
If you block off the return line and it holds,the FPR isnt leaking.Its the check valve in the pump.
One more thing to check,but usually isnt the cause,the cold start injector,if leaking,can cause a pressure drop.But Im betting my money on the check valve inside the pump.
Thread Starter
Pro
Joined: Nov 2005
Posts: 602
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From: North Bay Ontario
You might have a bad check valve in the fuel pump.
My old 86 did the same thing and a new Fuel pump fixed it.
If you block off the return line and it holds,the FPR isnt leaking.Its the check valve in the pump.
One more thing to check,but usually isnt the cause,the cold start injector,if leaking,can cause a pressure drop.But Im betting my money on the check valve inside the pump.
My old 86 did the same thing and a new Fuel pump fixed it.
If you block off the return line and it holds,the FPR isnt leaking.Its the check valve in the pump.
One more thing to check,but usually isnt the cause,the cold start injector,if leaking,can cause a pressure drop.But Im betting my money on the check valve inside the pump.
Thread Starter
Pro
Joined: Nov 2005
Posts: 602
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From: North Bay Ontario
With the return line already pinched, in order to hold pressure in the system, and then pinching the feed line the pressure goes up about 15 lbs. Releasing the pinch on the return line and the pressure drops to 0 in 30 seconds. I just installed a new fuel pump about 3 weeks ago. I've eliminated the fuel pump as any part of the problem.
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Thread Starter
Pro
Joined: Nov 2005
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From: North Bay Ontario
As I stated in the first post - I have a brand new FPR diaphram. Even with the old one, there was no fuel in the vacuum line. It's leaking at where the stainless steel disc seats on the FPR base.
Instructor
Joined: Aug 2009
Posts: 146
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From: Broadway Virginia
Would a batch of weak, (but new) , springs on the backside of the diaphragm cause this? If the mating surfaces of the disk and seat check out OK, is not the spring itself the only other suspect?
Advanced
Joined: Jun 2013
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I realize this thread is 9 years old but has anyone else had a leak where the stainless steel disc seats on the FPR base? I would like to see a pic and learn more. I wish pletzvet had told how the story ended? I have a similar problem, possibly but mine could be the diaphragm. I put a new diaphragm in mine though about 4 years ago.
