wicked383bird

iTrader: (2)

First off, I would like to say that I have read a few of the "low fuel pressure" threads using the search feature.

I am running an ls1 in a 1964 Chevelle SS, using the Ricks Hot Rod Shop Tank setup. My first issue was I didnt have enough voltage and amps at the pump. I am now way above what the pump requires with 14.7 volts at the pump, yet only getting 50psi fuel pressure at the fuel rail shrader valve. I am using the corvette style regulator/filter combo. I was told by Ricks hot rod shop, that the pump in this tank is an AC DELCO, that performs equivalent to a Walbro 255. Yet, I am still having low fuel pressure, and the pressure fluctuates with any amount of throttle given.

Does anyone have any input? Thanks A million!

Rodder

iTrader: (2)

using a real Delco filter/regulator or some other brand?

Is anything coming out the return line and going to the tank? If not, you have a bad pump. If you are getting return flow, then you have a bad regulator.

wicked383bird

iTrader: (2)

I replaced the filter, twice, with original AC Delco filter/regulator. There has to be return flow, because when I pinch the return line with vice grips, the fuel pressure shoots a little past 70psi. But still fluctuates with any throttle given.

Old Geezer

iTrader: (3)

Have you pulled the pump, and looked at how it's plumbed??

bczee

iTrader: (12)

There are case that if the hose coming from the pump is leaking will cause low pressure.. possible a lose clamp, split hose, etc..

I know you have pinched the return line and the pressure goes up.. but it is just one more thing to check when all else fails to be the problem.

wicked383bird

iTrader: (2)

Wouldnt the pump be the culprit if its only rated at 50psi, and thats all im getting?

bczee

iTrader: (12)

It could be, but like I said.. if you have a split in the hose, lose clamps, you would also lose pressure. Like I said, one more thing to check if you have too.

oange ss

iTrader: (50)

if you blocked the return and get a pressure rise then it's most likely not the pump, however after chaging the filter/reg already, the only thing left is plumbing...good luck

BanditDave

iTrader: (11)

Before you go crazy chasing a unicorn, take a step back and look at what you have changed. I would also recommend getting a reading just as the fuel is entering the fuel rail. I quickly skimmed through the thread and what are you using for fuel line??? I am using -6 throughout with a sumped stocker tank, Vette regulator, and a Walbro 255. It is pinned at 58 psi entering the fuel rail and barely dips under revs. Since all my lines are brand new the fuel pressure is rock solid. I am thinking maybe because you have the gauge where it is the fuel pressure might be slightly down since fuel is being spent. I am probably wrong but it is just a thought.

If you have the old lines that could definitely be an issue as well. What I suggest is that you connect the fuel lines to the fuel rail but leave the return line off and put it in a bucket. Fire her up and see what it reads. If it is still low then drop the tank and take a look at the pump. There may very well be something wrong with the whole pump set up. It is built by humans...we all screw up and your luck sounds like mine...haha.

Let me knwo what you find and best of luck!!!!

BanditDave

wicked383bird

iTrader: (2)

All the lines are brand new. We were initially going to use plastic line (like the impala ss) but instead ran a combo of rubber and steel braided fuel lines...

98Camarod

iTrader: (43)

Hell, if the lines are new and show no wear, I'd be pointing the finger at the pump.

wicked383bird

iTrader: (2)

update: I just realized I made a mistake. It is not a combo of rubber and braided lines. Its two lines, both braided hose, with fittings on both ends. There is no gas from anywhere on any of the fittings in the entire system.

Ricks Hot Rod shop gave me the part number to the Delco pump in the tank. AC DELCO EO381 (25163473). This is a standard pump on 1998 to 2002 ls1 equipped cars.

Please Help!

ssduane

iTrader: (3)

Does the engine not run good? How about the gage you are using? You should be getting 58 psi but are getting only 50, could be gage error?

Old Geezer

iTrader: (3)

What kind of gauge is it? Not the little silver dollar size, from Summit, Jegs, etc. is it?
I have tested MANY of those, on my inj bench. Have found them all the way from dead-on, to 5-7psi off, in either direction. You can use 1 of these gauges IF you know the error, and if it's consistent. Many I tested were like that. IE: off 3psi, but were that same 3psi all the way.
If it's a "cheapo", get a good gauge w/ a low error %, for the entire range.