Fuel pressue issue
Thread Starter
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
Fuel pressue issue
I have about 4000-5000 miles on my LPE fuel pump. It starts out with 60-62psi, but the longer I drive the car, the less pressure it makes. Last week when it was hot my pressure got down to 54psi.
And I noticed under boost, the pressure stays the same, even though I have my boost-up-pump turned up full.
Is my pump worn out already?
And I noticed under boost, the pressure stays the same, even though I have my boost-up-pump turned up full.
Is my pump worn out already?
Instructor
Joined: Feb 2005
Posts: 228
Likes: 2
From: Phoenix AZ
St. Jude Donor '08
Heat will reduce pressure a couple of lbs, as I have found out in Phoenix hot temps, but when my pressure dropped to the low 50's and wouldn't move I started to dig into it. I bought a new sensor, lengthened the line to take it away from the engine and nothing help. I finally bought a cheaper, different brand fuel pressure guage and it's back to 62. So I figure it must have been the Autometer guage.
Le Mans Master
Joined: Oct 2005
Posts: 7,088
Likes: 1,829
From: Metro Detroit Michigan
Happened to me (and others) with both LPE and Racetronix pumps since day one. My fuel press gauge has been replaced, (it was defective but problem is still there). Problem has gotten better with time (three years).
My guess is that there are some tight mechanical clearances in the fuel pump which bind when the fuel gets heated. A new pump (same kind) might only make it worse. Tried three so far.
My guess is that there are some tight mechanical clearances in the fuel pump which bind when the fuel gets heated. A new pump (same kind) might only make it worse. Tried three so far.
Thread Starter
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
I wonder if I can put a regulator before the fuel rail and set it to 54psi and tune the motor for that amount of pressue without a negative effect? And would the backpressure on the pump side cause any issues?
Le Mans Master
Joined: Oct 2005
Posts: 7,088
Likes: 1,829
From: Metro Detroit Michigan
Hmm, sounds like it might work, as long as your fuel pressure doesn't ever go below that. Mine did if I drove it long enough on a hot enough day. Would drop like a rock at max power.
Here's an older thread attempting to diagnose the fuel heating issue, and which also has detailed temperature charts.
LINK
Here's an older thread attempting to diagnose the fuel heating issue, and which also has detailed temperature charts.
LINK
Last edited by Warp Factor; Jul 6, 2008 at 07:30 AM.
Thread Starter
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
Hmm, sounds like it might work, as long as your fuel pressure doesn't ever go below that. Mine did if I drove it long enough on a hot enough day. Would drop like a rock at max power.
Here's an older thread attempting to diagnose the fuel heating issue, and which also has detailed temperature charts.
LINK
Here's an older thread attempting to diagnose the fuel heating issue, and which also has detailed temperature charts.
LINK
I think I may drill and tap the fuel rail and mount a mechanical gauge directly on the fuel rail and see if it jives with the electronic gauge. At least that will tell me if it's the gauge or not.
Last edited by RED99; Jul 6, 2008 at 10:53 AM.
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Melting Slicks
Joined: Dec 2003
Posts: 3,315
Likes: 17
From: Near Jacksonville Fl.
If it's an Autometer gage it's probably the sending unit, mine suddenly dropped 7 psi so I spoke with my tuner and he said they have replaced 7-8 sending units this year.
So I checked it with a mechanical gage and $100.00 later for a new sending unit it's back to 62 psi.
So I checked it with a mechanical gage and $100.00 later for a new sending unit it's back to 62 psi.
Thread Starter
Safety Car
Joined: Jul 2005
Posts: 4,275
Likes: 4
From: Vancouver WA
If it's an Autometer gage it's probably the sending unit, mine suddenly dropped 7 psi so I spoke with my tuner and he said they have replaced 7-8 sending units this year.
So I checked it with a mechanical gage and $100.00 later for a new sending unit it's back to 62 psi.
So I checked it with a mechanical gage and $100.00 later for a new sending unit it's back to 62 psi.