Fuel Pressure Question
Thread Starter
Racer
Joined: Aug 2007
Posts: 325
Likes: 0
From: South Dakota
Fuel Pressure Question
I recently installed autometer nexus gauges, my fuel pressure stays at about 62 pounds when the car is running. When I shut the car off drops to 54 pounds. After an hour or so if I turn the ignition on the fuel pressure shows 0. My question is this, does the fuel system bleed off over time or do I have a leak. I have checked all my lines and cant seem to find a leak anywhere. 
Safety Car
Joined: Aug 2007
Posts: 4,836
Likes: 9
From: Rushsylvania Ohio
Don't think you are getting an answer because to most guys on here it is a pretty silly question. I'll step up and try to help! No, there is nothing wrong with your fuel system and you DO NOT have a leak. There is a fuel pressure regulator on the car and when it is not running, it allows the pressure to bleed off. Sitting for awhile or overnight will typically bleed off all the pressure. Hope this helps!
Burning Brakes
Joined: Feb 2002
Posts: 1,232
Likes: 10
From: Montrose Colorado
I got the same gauge with a Maggie set up and the psi stays at 60 lbs. overnight, it does zero out if you push the start button, but don't start the car. I'm also using a Magna Volt so when you go into boost the pressure goes up to 62 to 65 lbs. I believe your fuel pressure regulator is in the fuel tank.
Racer
Joined: Aug 2007
Posts: 397
Likes: 0
From: East Longmeadow MA
in the tank
The fuel pressure regulator is in the tank. Specifically the one your concerned about is the main regulator on the fuel delivery module in the left hand tank.
The main thing causing the pressure drop is the big change in temp from a really hot environment while driving to a cold system when you go to start up much later. The system has only a little flexibility so a small volume change due to temp drop means big pressure change.
On top of that the pressure regulator is a metal on metal seal. The Corvette has the best regulator in the business with the best materials.... very expensive.
The good news is your car is normal and also the same tiny amount of volume change that dropped the pressure from 60 to zero raises it right back up to full pressure right when you hit the button!
The main thing causing the pressure drop is the big change in temp from a really hot environment while driving to a cold system when you go to start up much later. The system has only a little flexibility so a small volume change due to temp drop means big pressure change.
On top of that the pressure regulator is a metal on metal seal. The Corvette has the best regulator in the business with the best materials.... very expensive.
The good news is your car is normal and also the same tiny amount of volume change that dropped the pressure from 60 to zero raises it right back up to full pressure right when you hit the button!
Safety Car
Joined: Jun 2004
Posts: 3,563
Likes: 2
From: Dallas Tx
The spec is 55 - 62 with ign on fuel pump running. Then after key off it must not drop below 51 for 5 minutes. Sounds like yours is fine.
If it runs normal pressure with ign on, then drops below 51 within 5 minutes, the leak is leaky/dirty fuel injectors. A pressure regulator problem would cause a pressure problem with the ign on/ pump on.
If it runs normal pressure with ign on, then drops below 51 within 5 minutes, the leak is leaky/dirty fuel injectors. A pressure regulator problem would cause a pressure problem with the ign on/ pump on.
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Racer
Joined: Aug 2007
Posts: 397
Likes: 0
From: East Longmeadow MA
2 ends
The spec is 55 - 62 with ign on fuel pump running. Then after key off it must not drop below 51 for 5 minutes. Sounds like yours is fine.
If it runs normal pressure with ign on, then drops below 51 within 5 minutes, the leak is leaky/dirty fuel injectors. A pressure regulator problem would cause a pressure problem with the ign on/ pump on.
If it runs normal pressure with ign on, then drops below 51 within 5 minutes, the leak is leaky/dirty fuel injectors. A pressure regulator problem would cause a pressure problem with the ign on/ pump on.
The pump on problem Michrider mentions with the regulator is total failure of the diaphram.
