problems with fuel system

here is what i am running: fuel cell, walbro inline 255lph, corvette filter. last week i found some water in my gas tank after the truck started running real bad after it warmed up. it would fall all over itself under acceleration after a fwe minutes of driving.

i replaced the fuel filter, and found that when the truck started to run rough, it was because the fuel pressure was dropping to around 20. it would idle right at 60, then during acceleration, would fall to around 20, even from stop sign to stop sign in the neighborhood.

my buddy that tuned it thought that running the water through the pump had burned it up do to the water hindering the gas's lubricating ability.

so, yesterday, i replace the pump.

start it up, drive it around a bit, and after warming up, it starts bogging during moderate to heavy acceleration.

get home and put the fuel pressure gauge on it, and the damn thing is idling at almost 100psi:bash: so i havent driven it since.

i was under the impression that the corvette fuel filter was internally regulating. my buddy that did the tune doesnt think so, and says i need to put a hi-pressure fuel regulator on the system.:confused:

am i wrong about this filter and need to put a regulator on it? i thought after reading all of the conversion threads that this filter regulated at 58psi.

and would having TOO MUCH pressure cause it to act almost like it did when it wasnt getting enough?

i am about ready to just throw a carb on this thing

The filter should regulate your pressure at 58 psi. Any excess should should be bled back into the tank unless something is blocking the ability to bleed the pressure back into the tank. Check your return line for blockage. You have the fuel pump hooked into the 3/8" side of the regulator, correct?

i am about to leave work and will double check when i get home, but i am pretty sure it is.

i mean, it was staying at 58-60 yesterday, and i didnt touch the filter when i installed the pump. the filter is hooked up the same.

but i will look in a few minutes.

the line from the pump is going to the inlet on the filter that is on the side, not the inlet right in the middle of the filter.

and i took the gauge off, put it back on, checked the pressure again. when i turn the key to the on position, and the pump primes, it goes to 80psi.

when i start the truck, it goes to 98 and stay there as it idles.

i do not understand. it was keeping it at 58 with the old pump, why not now.

is there any possible way of hooking the pump up wrong and causing this? if there is, then i could do it.

Okay, the pump is feeding fuel to the inlet on the end of the fuel filter that has two fittings on one end and it is the larger of the two connections? The smaller one next to it is returning back to the fuel cell? The other end of the filter only has one 3/8" line going up to the engine?

yes, the pump is feeding the larger of the two inlets. the smaller one goes back to the fuel cell. and the other end of the filter, with the one outlet, is going to the fuel rail.

Check the return line and see if the pressure isn't bleeding back into the fuel cell for some reason. Sounds like something isn't working correctly, fuel filter or blockage in the return lines. Didn't you replace the filter recently? Do you have the old filter to try so you can see if you have a defective filter?

yes, i replaced the filter before i replaced the pump. i will throw the old filter on today and see what happens.

thanks

well, i took the return line off the back of the filter, and yes its hillbilly, but i blew into the return line and could hear the fuel in the cell bubbling.

so then i leave the return line off, and turn the ignition to "ON" and when the pump primes, it fluctuates betwen 50 and 60psi. not up to the 80 that it would prime at last night.

so not sure of there was something clogging the return line, or possibly clogging the return outlet on the filter, but i am going to hook the return back up and start it when all the gas dries up.

this is still with the new filter too.

hook everything back up, prime the pump, primes right at 60, happy.

start it, and immediately it goes to 100+ and stays there as it idles, pissed.

gonna put the old filter on next and see what that will do.

Do you have a voltage regulator problem? What is the voltage with engine off vs. engine running? You may be doing the boost-a-pump trick and the return line is too small to handle the flow amount increase created by additonal voltage.

i put the old filter on and same thing. primed to 60, then went over 100 when i start it.

i do not have a volt meter to see if there is to much voltage. what would cause that to happen though? i have checked all the connections, they all seem to be good.

but that was my first thought when i first installed the new pump, was that i hooked something up wrong and it was getting way too much voltage.

i am done with it today. but will be back tomorrow to try anything else somoene recommends.

seriously, that edelbrock/msd carb combo is looking very tempting right now.

Another issue could be restriction in the return line. If the hole through any of the return line fittings is smaller than the hole coming out of the filter/regulator, you have introduced a new regulator to the fuel supply.

A digital voltmeter can be had at Walmart for about $10.

see, that makes sense to me too, a restriction in the return line. but then when i remember that before i put the new pump on, it idled at 60 psi, makes me wonder how a restriction could occur when all i did was replace the pump and never touched the return line.

i will pick up a voltmeter tonight and see if that has something to do with it.

you could have had a weak pump before. Oh yeah, matter of fact you did have a weak pump before. :whack:

yeah, yeah...my head is not clear right now, about to blow smoke out of my ears.

i have a buddy that says he will come over next week and look at and probably replace the fuel lines. hopefully that is where the problem is.

thanks for the help red, newbies like me really do appreciate it...lol

i will check the voltage tonight when i get off work.

Get a piece of 5/16" hose about 5' long and slip it onto the return side of the filter and put the other end in a gas can. Start the truck and watch your pressure. Oh yeah, plug the return line or elevate the end above the fuel tank so you don't make a big mess on the ground. :laugh:

will do, thanks again

well, tried the voltmeter and it was right at 12.

guess i am going to try the hose into a bucket next, and if that dont work, i am not sure what to do next.

i have a buddy that says he will come over and help me install a regulator with return lines and such...may just go that route.

how do the f-bodies regulate fuel pressure? evidently its not at the fuel rail, so how do they do it?

Start the truck and see what the voltage is at the alternator lug.

The Fbody uses a regulator built into the tank, pretty much the same idea as the Corvette fuel filter but it's in the tank.

i am sorry man, but i cant find any readings off of the alternator. where should the probes be put?

and the reading i posted earlier was at the posts on the pump while the truck was running.

At the large lug where the main alternator wire connects. Start the engine and check the voltage there with ground on the alternator body.

man, if you are talking about where the wire connects on the back of the alternator, then i cant get to it without taking the alternator off. i can barely see it, and there is no way i can get my hand and the probe close enough to touch it.

Quote:

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Originally Posted by RedHeartbeat

Get a piece of 5/16" hose about 5' long and slip it onto the return side of the filter and put the other end in a gas can. Start the truck and watch your pressure. Oh yeah, plug the return line or elevate the end above the fuel tank so you don't make a big mess on the ground. :laugh:

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tah dah...did it this morning and it is idling right at 60:) is that ok though? the first time i had a small piece of 3/8 hose on it and it was idling at 57, then went and bought a long peice of 5/16, slipped it on, and it was at 60.

now i need to find an adapter to go from the 5/16 to the 1/2" hose i have coming off of the fuel cell.

thanks red, took a week but finally got it. hopefully now, when i can drive it, the stumbles are gone too.

Now that you've seen what restriction can do to your pressure, be sure the fitting you buy doesn't have a small hole in it. A steel threaded adapter will be thinner wall than doing it with brass fittings.

Glad you got it figured out man.

thanks...put the fittings on today and it was at 57-58...even drove around for about 25 minutes, and no problems.

need to get the posi installed and another touch up tune and it should be ready to roll

:thumb: