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What could cause my fuel pressure to drop?
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alfordaln Offline
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What could cause my fuel pressure to drop?
I have a 1990 chevy camaro rs. swapped the FI 305 for a carb. 355(bored 30 over). When I swapped engines I kept the electric fuel pump and installed a regulator. My ca kept dying no matter what I did so hooked up a fuel pump vacuum meter or whatever it's called and this is what I found: with fuel regulator on it reads only 1.5 psi while running and drops to 0 then car dies, without fuel regulator it reads 3psi then drops to 0 while running, for everytime I turn the key to on position w/o regulator it raises psi by 3 or 4, if I turn key to on position 3 times it will read 10-12 psi then I started the car and it ran perfectly until it got down to 1 and 0 psi then it dies, the more I rev the engine the quicker the psi drops to 0. So what could cause my fuel pressure to drop so rapidly? It can't be the fuel pump or fuel filter cause I just replaced them cause thats what i figured it was.

Would you be my valentine?
01-12-2010 11:06 PM
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thomasbala Offline
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RE: What could cause my fuel pressure to drop?
(01-12-2010 11:06 PM)alfordaln Wrote:  I have a 1990 chevy camaro rs. swapped the FI 305 for a carb. 355(bored 30 over). When I swapped engines I kept the electric fuel pump and installed a regulator. My ca kept dying no matter what I did so hooked up a fuel pump vacuum meter or whatever it's called and this is what I found: with fuel regulator on it reads only 1.5 psi while running and drops to 0 then car dies, without fuel regulator it reads 3psi then drops to 0 while running, for everytime I turn the key to on position w/o regulator it raises psi by 3 or 4, if I turn key to on position 3 times it will read 10-12 psi then I started the car and it ran perfectly until it got down to 1 and 0 psi then it dies, the more I rev the engine the quicker the psi drops to 0. So what could cause my fuel pressure to drop so rapidly? It can't be the fuel pump or fuel filter cause I just replaced them cause thats what i figured it was.
The old mechanical fuel pumps put out about 7 to 9 psi. What did you do to the original fuel pressure regulator; the one that connected to the injector fuel rail? Is it still on? Where in line did you put your new regulator, before or after the old regulator? It's obvious your engine is starving for fuel. If you left the old regulator on, the pump shuts off when it reaches 30 psi; when you crank and run for a few seconds the second regulator lets some gas through but not enough so the regulator builds back up to 30 psi and shuts off the fuel supply. If you can't figure out how to regulate the system (it may be impossible to use a 30 psi pump anyway) you'll have to spring for a lower psi pump made for carburated engines. Trying to make old tech work with new tech is always a big problem and sometimes just can't be done.
01-13-2010 06:16 PM
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