help with fuel pressue
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
help with fuel pressue 11/20 update
ok guys i need some help here is what i did, lt1 intake on 90 L98 finally got it done i have a aeromotive afpr that is plumbed in on return line. car has 24# inj. and jesse did a chip for it ran pretty good before swap, anyway started car up running rich and fuel pressure on gauge is 80 pounds pressure stays there even if i turn adj. screw clear up to where there is no pressure on spring car is prob not timed right but that should not have anything to do with pressure anybody got any answers please let me know. can fuel pressure be changed by chip thanks for any help geo.
Last edited by geogolf; Nov 20, 2007 at 08:43 PM.
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
pressure
twisted i dont have another gauge but it is a new gauge not that it cant be bad i doubt reg is bad i tore it apart and only thing that could go bad is rubber diaphram just does not make sense
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
pressure
paul the return line was ok before swap so i dont think that is prob. i wll check it. reg is not bad there is nothing in it but a rubber diaphram and a spring unless there is more to it than i can see like i said pressure should be real low with adj screw clear out stumped 
Race Director
Joined: Sep 2000
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From: The Top of Utah
The fuel pressure is caused by a restriction in the return line. The regulator is a variable restriction, placed where it is, for the express purpose of CAUSING fuel pressure. The problem is an excess restriction (80# sounds like a total blockage) in the fuel system, somewhere between the gauge connection and on back through the fuel system, through the return line to the tank. It just about can't be anywhere else.
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Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
pressure
cfi here is what did i ran inlet fuel line into pass. side of rail then ran line from driver side rail fitting to reg. that is on a bracket by firewall gauge is plumbed into the 1/8 port on side of reg. return line goes out of bottom of reg. back to tank is that how it done or not. could not connect reg. the way it is on a lt1 car because of lack of space i used the stock distb and there is not room for reg. return line is 5/8 high pressure hos until it gets to hard line that was there
Last edited by geogolf; Nov 10, 2007 at 06:27 PM.
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Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
think i found prob
guys i took reg apart again and saw that the vaccum port was screwed in past flush and was causing spring not to go into diaphram, it was compressing but not against diaphram but the vaccum port that was between the coils of spring hope that was prob thanks for replys geo.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by geogolf
cfi could fuel line be to small it is 5/8 fuel line i can tear fuel return line off and check but like i said it ran fine before swap
Stop and think. What makes fuel pressure in the fuel system? Pressure in ANY hydraulic system, for that matter. My previous post (#6) alluded to it. Pressure is caused by resistance to flow. If it weren't for the fuel pressure regulator providing the resistance to flow in the stock system, gasoline would shoot through the fuel system like the proverbial "stuff" through a tin horn. And with all that rapid flow, there would be almost no fuel pressure. Now apply that knowledge to your fuel system. If there were no resistance to the fuel flow, between the pressure gauge and the fuel tank, you would have no pressure reading. The regulator is an adjustable device that allows you to vary the resistance to the fuel flow and consequentially the fuel pressure. Somewhere beyond where the gauge is connected, you have a blockage, a kinked hose or line, or SOMETHING that is causing all that pressure. Just for giggles, pull the return line off at the tank. Is there any fuel returning? Think of the principles involved and apply some common sense. You'll find the problem.
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Race Director
Joined: Sep 2000
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From: The Top of Utah
Problems become easier to find and solve when you apply the principles of operation and some common sense to the diagnostics. Even when you told him what the problem was, he countered with denials. I got the same response, so I thought maybe knowing how it worked might help.
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Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
pressure
heys guys not trying to argue but checked that return line there is no kink i still think that the reg was hanging up when i was trying to drop pressure will have to check tomorrow thanks for your help geo.will post what i find be it whatever
Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
return line
cfi/paul pulled return line off at tank turned pump on three times first time fuel ran out but not as much as 2/3 time, could line have been vapor locked or have air bubble 2/3 time full flow i still think reg. spring was hanging up on vac. port and not releasing got to wait for my reg. fittings ther i can button her up and try again thanks for you help geo.
Race Director
Joined: Sep 2000
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From: The Top of Utah
I got a headache last night trying to read one of your posts. With no caps and no periods at the end of sentences (are there sentences in that mess?, it is very difficult to separate where one thought starts and the other stops, if that is actually happening. Reread my posts. There is a restriction between where the gauge is connected and the fuel tank. That includes the regulator. There ARE no arguments. You have been given the principle, you can find the blockage.
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Thread Starter
Drifting
Joined: Jun 2005
Posts: 1,426
Likes: 1
From: brookville pa.
cfi
you being the genius you are, i can understand why you could not figure out what i had asked help with. i will make it simple for you i wont answer your posts and you sure as hell dont have to answer mine
Team Owner
Joined: Feb 2006
Posts: 23,153
Likes: 117
From: San Antonio Texas
Make it simple. When you have the reg. off the car, blow through it. Should be no air or very little. Put a vacuum pump on the vac port and blow through it again. It should have no restriction. If it still doesn't flow with vacuum on the port it's a bad regulator. If the regulator is OK then the return line is restricted or something is plummed wrong.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by geogolf
you being the genius you are, i can understand why you could not figure out what i had asked help with. i will make it simple for you i wont answer your posts and you sure as hell dont have to answer mine
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