Fuel Pressure problem....

[rposton1]

Looking for some help on this one, I have low fuel pump pressure, I have replaced 2 pumps, removed check valves from tank, replaced fuel filter and checked every line for restictions. What happens is my fuel pressure goes from 5psi to 1psi no matter what tank it is on, its strange at times its ok then it goes down. I have done some WoT runs and my bowls seem to be full still, but I do see some bubbles. My pump is an electic Carter 100gph 7psi
vane type, its on a BBC 502 . thanks in advance Rob

[FASTRAT]

Looking for some help on this one, I have low fuel pump pressure, I have replaced 2 pumps, removed check valves from tank, replaced fuel filter and checked every line for restictions. What happens is my fuel pressure goes from 5psi to 1psi no matter what tank it is on, its strange at times its ok then it goes down. I have done some WoT runs and my bowls seem to be full still, but I do see some bubbles. My pump is an electic Carter 100gph 7psi
vane type, its on a BBC 502 . thanks in advance Rob
get rid of the electric pump!!!...get a good mech pump & ck ur fuel tanks for vents!!
fastrat

[rposton1]

Yeah hehe only problem its a Gen6 block, yeah vents are good on both tanks....Rob

[Moneypitt]

Remember, electric pumps are pushers. They don't pull all that well. How is the plumbing set up? I found some 5/16ths line pick ups in boat tanks. Thats 1/4 ID !!!!!!!!! Changed that and cured it. The Coast Guard doesn't like bottom dump tanks, but they sure work better than the ones you have to pull the gas out the top of.......MP

[dtr352]

Is it a mechanical or elictric fuel pressure gauge. If electrical it could just be a voltage issue. Just a guess.

[rposton1]

just checked looks like all my fuel line is 3/8 and my pick up tubes are about the same, also want to add its higher when I start the boat then after I drive for a while it goes down. Rob

[WHATA SQUIRT]

Have you checked the gauge?

[rposton1]

Its a brand new guage, but I guess your right it could be bad but it only seems to happen after it warms up...

[Havasu Hangin']

I'd make sure it's not sucking air. The fitting on the tank to the pickup tubes is a good place to start.

[rposton1]

I'd make sure it's not sucking air. The fitting on the tank to the pickup tubes is a good place to start.
looks to be one piece how would I check that...rob

[Moneypitt]

OK, I've heard of several different problems where the electric pump actually heats up due to lack of circulation of fuel. It seems when the pump comes up against a regulator, and/or float bowls, the fuel stops moving. The fix is to install a by pass, simular to the ones used on injected engines with cam driven pumps. Set the by pass to 7 lbs. and allow the fuel to return to the tank. This has shown to keep the pump cooler, and cured alot of fuel delivery problems..........MP

[Paul128a]

I had the same problem on my 350 chevy. I ran two mechanical pumps and lost fuel pressure on top, my sparkplugs would turn scary white, and RPM was limited to 4000.
I replaced all the fuel tubes going in the tank to 3/8s, used 3/8's hose all the way to the carb. I also added two more 5/16 fuel tank breathers so that the tank will not vacuum. That cured it.
However, I now run a Holley Blue electric pump set at 8psi.

[bakerjet]

the carter pump would not keep up with my mild 454 i had the same one it is a pos i went round and round with it and finally pitched it and bought a mallory comp 140 problem gone. oh yea be sure to run a return style regulator maa-4309 and not the dead head reg. if you dont have a return port on your tank just tee it back into the suction of your pump and it will be fine.

[rposton1]

Thanks all I just ordered the Mallory wish me luck....Rob