LOW Fuel Pressure
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From: CA
LOW Fuel Pressure
i cant seem to get my fuel pressure above 25psi. a few months back i took the intake and fuel rails off to fix my leaky intake gasket now that its all back together i have a low fuel pressure issue. when i hook up a gauge to the schrater valve when with the car on but the ignintion off i get 23 or so... if i start the car up i get 25psi but my needle jumps around a bit. when i let off the gas the car dies.... i have a new fuel filter, took the fuel pump out to inspect and bench test and all seems to be good (it turns on when you apply 12volts to it). why is my fuel pressure so low. is it adjustable (my car is stock)
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i cant seem to get my fuel pressure above 25psi. a few months back i took the intake and fuel rails off to fix my leaky intake gasket now that its all back together i have a low fuel pressure issue. when i hook up a gauge to the schrater valve when with the car on but the ignintion off i get 23 or so... if i start the car up i get 25psi but my needle jumps around a bit. when i let off the gas the car dies.... i have a new fuel filter, took the fuel pump out to inspect and bench test and all seems to be good (it turns on when you apply 12volts to it). why is my fuel pressure so low. is it adjustable (my car is stock)
If its steady so is the pressure and flow. If its bouncing around....so is the pressure and flow rate.
Your regulator is dumping the vol and half the pressure. It can leak internally and send all that flow back thru the return line. You can pinch off the return line somewhere and see if that effects the pressure any.
Safety Car
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it always amazed me at how stupid simple the regulator is and how much it cost...
Corvette Tax.
Look at the disc on the spring/plunger. Sometimes that will have a ding or some evidence that its not seating and allowing fuel to bypass straight to the return instead of the rails.
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From: CA
Team Owner
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From: Summerland B.C. Canada
Put on gauge and pinch return line closed. You can pinch the line if you remove gas filler door and rubber boot or try and access the rubber portion below AC compressor.
Read this >> http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Read this >> http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
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Thread Starter
Pro
Joined: Jun 2010
Posts: 535
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From: CA
Put on gauge and pinch return line closed. You can pinch the line if you remove gas filler door and rubber boot or try and access the rubber portion below AC compressor.
Read this >> http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
Read this >> http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
OK i went out and removed the rubber boot and fuel door, pinched the return line with a cloth, pair of pliers and a vice grip. checked the gauge 23psi started the car 25 or so psi.... does that mean my pump is weak or does that mean my fuel pressure regulator is done?
Safety Car
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OK i went out and removed the rubber boot and fuel door, pinched the return line with a cloth, pair of pliers and a vice grip. checked the gauge 23psi started the car 25 or so psi.... does that mean my pump is weak or does that mean my fuel pressure regulator is done?
Positive it was the return that was pinched and not the vapor line?
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If the return line was pinched off, and the gauge was on the rails, and the pump was running, there is no place for the fuel to go so it should build up max pressure. If its not, then work backward from the motor, fuel filter, sock on the pump(very good for plugging) and finally the pump itself. The regulator is most likely good. Even when it leaks internally the pinched line prevents it from freeflowing to the tank and pressure builds...should. If it does not then that means the pressure was/is never there to begin with. Pump, filter or sock.
Positive it was the return that was pinched and not the vapor line?
Positive it was the return that was pinched and not the vapor line?
Team Owner
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From: Summerland B.C. Canada
A leaky pulsator(directly above pump) would also cause low pressure. You have the door off, you may want to pull the pump and replace the pulsator with a piece of fuel injection hose and 2 stainless clamps and see if that helps, before you buy a pump. 
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thanks im going to do that now... u know i had to cut the fuel feed line in order to get it off to get the pump out last time i took the pump out so when i re installed the pump i cut a new line and attatched it to the old line with a 3/8" fuel line joiner (u know the gold metal tube with stepdowns). if i used the wrong size joiner would that affect my fuel pressure?
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ok so i took the pulsator off put the pump back in and it still read 25psi.... so i took the pump out, bought a new one, put the new one in and now i get 40psi... So low Fuel pressure can be caused by a fuel pump starting to go bad... thanks all
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1st Gear
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From: Rockford Illinois
I have a 1996 Collectors Edition with the LT4 engine. After driving and letting it sit for a while it was hard to start and missed a lot. The fuel pressure was 10psi with ignition on and motor not running. With motor running the reading was 24psi regardless of rpm.
I first replaced the Fuel Pressure Regulator, no change. Then the fuel filter, again no change. Finally I replaced the Fuel Pump and now with ignition on and motor not running 43psi initially then drops to 38psi.
With motor running its 38psi and when I rev it the psi instantly increases to 43psi. Hard restarts when warm are a thing of the past. It's a real pleasure to drive.
I bought the car used with 70,000 miles and didn't know the fuel pump was failing.
I first replaced the Fuel Pressure Regulator, no change. Then the fuel filter, again no change. Finally I replaced the Fuel Pump and now with ignition on and motor not running 43psi initially then drops to 38psi.
With motor running its 38psi and when I rev it the psi instantly increases to 43psi. Hard restarts when warm are a thing of the past. It's a real pleasure to drive.
I bought the car used with 70,000 miles and didn't know the fuel pump was failing.
Last edited by Kerfer; Jul 8, 2012 at 07:01 PM. Reason: spelling
