What could cause my fuel pressure to drop?

Question

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. Everything ran smoothly after the engine swap for about 5 months and then I started having this prob.

Additional Details

4 hours ago
Only thing I can think of is maybe theres a sensor that isn't recieving any input so it thinks the car is off therefore shutting the fuel pump off. How would I bypass this(in detail)

Answer 1

the problem with it is you don't have a return line on it ,you cant use the pump in the tank i just got done changing one over ,without a return line the pump will lock up and stop pumping.this will also burn the pump up in no time ,you cant run that pump with that set up,you have to go external pump with a regulator on it,they don't need a return,the one you have in the tank will not operate without a return line,and you no longer have that with a carburetor set up,i been through this for about a week,good luck with it.,,PS you,ll have to change the sending unit also,i did on mine,but it runs fine now,good luck.

Answer 2

Could be the pressure regulator is hooked up backwards, or the pump just can't supply enough volume to maintain pressure. Or maybe the filter is blocked (this is common - bits of crap inside the fuel lines shake loose when you're working on the fuel system, then clog the filter.)

Answer 3

Sounds pretty simple. You should have about 10 psi fuel pressure. Something wrong at discharge or intake of fuel pump. Can't be there to help so forget starting engine and find why you don't have 10 psi

Answer 4

Clogged fuel filter--it ran OK and now it isn't ---something is clogged or it wouldn't have run at all. Talk to a shop tech that knows what he is doing with fuel systems. Maybe the regulator went bad or the pump is inadequate...it does happen. Good luck

Answer 5

i think of mad mav is stable. the pump is barely working once you first turn on the ignition and particular once you crank it and then the pump stops working. in case you DO get the pump to run that is prone to over means the carb and flood it. a extra perfect answer is to get an electric powered gasoline feed pump that's nicely matched with a carb. the FI pump is severe flow and severe tension.

Answer 6

Could there be a in tank fuel filter sock ?

Answer 7

Sounds like the regulator is installed backward -- who knows?

Answer 8

F.I. runs a closed system because of pressure,try a different gas cap that won't build pressure.