fuel pressure test

vrg3 · Post by **vrg3** » Tue Feb 21, 2006 4:01 am

I don't know what is wrong. If I were you I'd do the fuel-hose-to-a-gas-can test. Just be careful; gasoline is no joke.

Post by **Legacy777** » Wed Feb 22, 2006 12:55 am

Here's my pressures with the walbro pump

I got 30 psig at idle with the vacuum hose connected to the regulator. I got 40 psig at idle with the vacuum hose disconnected from the regulator.

Got them from this thread
http://bbs.legacycentral.org/viewtopic. ... l+pressure

I thought I tested the pressures on my n/a motor....going to look for them.

The Scooby · Post by **The Scooby** » Wed Feb 22, 2006 2:06 am

ya i talked with a tech at my work, he said he HIGHLY doubts the return line is clogged... simply because of its size, he is voting for the FPR, told me to hook up my pressure gauge again, is pressure jumps 10 psi then its good... if it doesn't its bad... so im heading outside to check her out again. wish me luck

The Scooby · Post by **The Scooby** » Wed Feb 22, 2006 3:42 am

ok well the FPR is good. ive also changed out the coil and ignitor unit to no avail.

i am lost... the fuel that came out of the filter was pretty nasty, not clear but was yellow and dirty looking and that what was comming out of the fuel filter, i hooked up my gauge after the filter in the engine bay and when i hit the relise button on it to expell the pressure the gas that came out was pretty nasty looking. i think im going to pull the pump and check the sock, maybe some day ill have some luck.

the way its going im thinking of selling this car and using that money to fix that tranny in my 91 and just build the 91

vrg3 · Post by **vrg3** » Wed Feb 22, 2006 4:05 am

The Scooby wrote:told me to hook up my pressure gauge again, is pressure jumps 10 psi then its good... if it doesn't its bad...

I don't understand what this means.

So he thinks that a 25 psi difference between idle (~5psia) and full boost (~25 psia) is okay? Cuz I don't even see how that's possible with a good FPR and return path.

That's odd that the fuel coming out of your filter was dirty, especially since you've recently replaced the filter.

The Scooby · Post by **The Scooby** » Thu Feb 23, 2006 3:25 am

no he ment that if its at 36psi, which mine is at idle, that it should jump up 10 psi when the vacume hose is disconnected, which it did.

also what should the fuel sock look like when i take out the pump, i just removed the pump from the tank tonight and the sock is black in some areas and yellow in the rest. also can i just buy a sock, they sell just the sock made by carter at schucks. if i cant then im just gonna buy a walbro 255 and say screw it.

vrg3 · Post by **vrg3** » Thu Feb 23, 2006 3:37 am

Okay, I didn't catch that you tried disconnecting the vacuum hose and saw it rise 10 psi. All I saw was this:

The Scooby wrote:idle was around 35psi. brake torqued it and it hit 60 psi at 10/11psi of boost.

...which still seems wrong. And 36 psi at idle still seems higher than it should be.

The sock shouldn't be black and yellow... at least none of the ones I've seen were.

The Scooby · Post by **The Scooby** » Thu Feb 23, 2006 3:51 am

ya it is sitting at 36psi at idle, went to about 45 with the vacume hose disconnected from the FPR... and under boost 10psi, it hits around 50...

so im off to buy a fuel pump sock right now...

The Scooby · Post by **The Scooby** » Fri Feb 24, 2006 3:01 am

is it possible that it is clogged fuel injectors? i put in a new sock filter last night, to no avail... im really getting tired of farching around with this and im really thinking of selling this car and keeping the 5sp 91 i bought.

also could it be running too rich because of the high fuel pressure? and that be causing the problem im having, also how could i make the car drop the pressure down to within specs?

vrg3 · Post by **vrg3** » Fri Feb 24, 2006 3:53 am

You said the FPR was good -- how did you verify that?

The fuel pressure does seem to be high, which would cause rich fuel mixtures. Generally, high fuel pressure is due to a bad FPR or to a clog in the fuel return line, so ... you get the pressure down to specs by fixing whichever of those it is.

The Scooby · Post by **The Scooby** » Sun Feb 26, 2006 4:23 am

well i checked the specs today on alldata, idle is 36psi, which is where mine is at, so it has the correct fuel pressure.

im just gonna take her into Walker Subaru next tuesday, drop her off in the morning and pick it up when i get off work. i talked with them and since im a tech at Sound ford i get a discount on parts and a free loaner car of my choice... STi here i come

vrg3 · Post by **vrg3** » Sun Feb 26, 2006 4:31 am

Hmm, Alldata seems to disagree with the FSM then.

Loaner STi?! Sweet!

The Scooby · Post by **The Scooby** » Sun Feb 26, 2006 10:20 pm

well ether way there is a problem with my car, if it does have 10psi higher then normal, then walker can fixer right up in time for the dyno at Torque Freaks next month.

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fuel pressure test