Well finally got around to installing the electronic Fuel Pressure gauge along with an EGT gauge to replace the rainbow a/f gauge.

At idle my fuel pressure shows 33psi. I thought this should be near 50 with the walbro 255lph fuel pump? Or am I totally wrong there?

Now heres the MAJOR problems im seeing. I went for a few sprinted runs.

At 7psi of boost my fuel pressure never got higher than 42psi. Yea thats a problem for sure and then compounded by the fact that I was in 3rd while doing the run and saw my EGT go upto about 1600F. So I cut it immediately. Lord knows if I melted anything, but as far as I know the car runs fine after that. Lets worry about later, Im more concerned about why Im only getting 42psi fuel pressure?

Is it the walbro 255lph pump in the tank that is jacked up? Or is the FMU jacked up?

BTW Im running a t3/t4 turbo, 10:1 Vortech FMU, GSS342 Walbro 255lph fuel pump and all my gauges are Autometer.

Dixit

 

are you running the oem fuel pressure regulator or an aftermarket fpr(in addition to vortech fmu)?

have you checked the fuel lines for kinks and routing in and out of the fmu?

how old is the fuel filter?

 

Yes the OEM one is still inline. I just left it there from when I was supercharged, why am I suppose to remove the oem one? I thought you need the OEM one for normal driving without boost and then the FMU Vortech kicks in when we start boosting.

Dixit

 

that is correct.. i edited top post for other things besides the walbro.. oh,, and check the vacuum lines on the oem fpr and the fmu.

 

The fuel lines for sure has no kinks since it only goes about 1ft from there to the fuel rail.

Fuel Filter is about 18k. I put the walbro back when it had maybe 14k. Fuel filter on the 5th gens is actually part of the entire fuel pump assembly.

Dixit

 

while the car is at idle, pull off the vacuum line from the OEM fpr and see if the fuel pressure goes up. also where did you tap in for your fuel pressure gauge?

 

The fuel pressure gauge is tapped on the fuel supply line. I got the fuel pressure sending unit right before it hits the OEM fuel pressure regulator.

So pull the vacuum line off the oem fpr and see if the fuel pressure gauge goes up? Should the car idle wierd at that point then?

Dixit

 

idle should change for a split second, just put your thumb on the vacuum line to plug the leak.

 

Sorry for my ignorance but Im missing you on one thing. If I take this vacuum line off the OEM FPR, then you want to go check the FP gauge inside? Or you want me to remove this line and plug it (which end? the line or the oem FPR?) and then have someone check the FP gauge?

Dixit

 

ah, don't worry about pluggin it if you're just doin it yourself. all you want to see is if the FPR bumps up fuel pressure when there is no vacuum. so just pull the line off and look at the gauge in the car.

 

Can't remember if I had asked you this before but how sure are you that you have got the correct fuel pressure regulator? The 2K+ regulators and fuel system are different from 95-99. The most confusing thing is that there is something that looks like the FPR and is located in the same place as the 95-99 FPR but is NOT the regulator. If I have mentioned this before I apologize for the repetition.

 

Fuel dampener.

 

Hehe! Thanks, I couldn't remember for a second.

 

No go answer my GT turbo question!

 

Still dont know why Im pushing tops maybe 50psi on the FP at 5psi boost. That was this mornings reading coming to work.

Dixit

 

Are you sure you are not using the 6:1 disc?

~50 psi is awfully close to what a 6:1 disc would put out at 5 psi boost.

 

Dixit,

I had PM'd you about this before but you didnt respond. My Turbo is now about 90% done. Yesterday we had trouble w/the Walbro Fuel Pump. I know it is not a direct fit but I have'nt been able to get a straight answer from any 5th Gen guys in months about the install of the damn thing! Anyway... We had a horrible time getting it to fit in the fuel pump unit.... the major issue was that one of the hoses that connects the Walbro to the fuel pump unit, seemed to be getting pinched to where not enough fuel was getting through and the car would'nt start...and the way the mechanism is set-up, there really no way to give that hose enough space to where the fuel can flow through it freely! Maybe I'm wrong I dont know and I need help... Dixit, since you are using the Walbro, maybe you should check this issue as well since you are having fuel flow issues. Kev, Dixit, whoever else has the Walbro installed on their 5th Gen...PM me and let me know the best way to install it ASAP.... Thanx.

Deac

 

Can you take a pic of what you're talking about?

 

Check out LatinMax's website. He did a pretty good write-up on the Walbro pump install on his 5thgen

 

Sorry if I never responded, appologize. Now I seem to lose you when you say there is a hose that hooks upto the walbro. When you remove the stock pump, it basically slides out of the plastic assembly and the top part of it has the "tire valve" style end. That is the same on the walbro, you just stick the pump back up in there. There are two tabs that may need to be shaved to resolve the issue of getting it all the way up there.

The bottom of the fuel pump has a small debris filter that attached to it, the one coming off the stock one doesnt fit the walbro, you have to use the walbro one. besides that, I never disconnected any hoses inside the fuel pump assembly except the ones at the top to get it out of the tank.

Dixit

 

Shouldn't Hal be able to clear all this up for you?

 

His invoice shows a 10:1 was given, now that dont mean Vortech couldnt have made a mistake. I need to open and check it.

Dixit

 

Where did you locate your EGT probe in the exhaust?

 

Right below the flange off the fedspec header. Basically within 6" of the exhaust flow. Autometer suggest that is the best and a few others recommended it, I know everyone WANTS to have it in the header, but this is where I put mine.

Dixit

 

I had a similiar problem, opened up my fmu and found a restriction.

 

Front or rear?

Fedspec header? Did you do a conversion?

 

yea front, had to remove the calispec precat as well as change the header to fedspec since the calispec header has a 6bolt flange instead of the standard 3bolt flange.

Dixit

 

That's useful information. Have you stated that before?

If so, sorry I didn't catch it.

 

on the front it routes backwards, so unless you want a uturned uppipe/ypipe, it must be switched.. then you must move the 2 o2 sensors for the precat, behind the real cat.

 

Thanks...I've been looking under a 4th gen too much lately. I forgot.

I'm hesitant to move the 02, I wonder if the front manifold could be cut/shortened right after the cat so they 02 can stay in place.

 

 

No hesitation needed on moving the O2s, I moved the lower ones to behind the main cat and that keeps the SES from coming on. No problems for sure. Only issue is that I cant put a testpipe in now. If I REALLY want to, then I have to get an O2 simulator or build one to keep the SES from coming on.

Dixit

 

 

Alright opened the FMU, definetely had a 10:1 disc in there. But Now I cant remember for the life of me whether there was a spring in the FMU holding the disc back or not? Is there just a ring and the disc in there?

Also I disconnected the OEM Fuel Pressure Regulator vacuum line and I saw the FP at idle go from about 35 to about 43-45psi.

So what we all think it can be now? Definetely running lean on top end even at 5psi.

Dixit

 

Considering you're getting 43-45psi at idle with the line removed vs. 42psi at 7psi, your FMU must not be working.

Double check the lines. Sorry, but I skipped that part of the install, so I can't be much help.

 

http://www.bigdogjonx.com/fullpics/turbo/fmulines.jpg That is the hookup of the FMU

http://www.bigdogjonx.com/fullpics/turbo/fuellines.jpg That is the vacuum lines and Ts and what not.

Also, did the FMU inside have a spring in it? I cant remember for the life of me when i opened my last one with the s/c.

Dixit

 

No... no springs. Just the blue diaphragam the thick circular disc and the flat round washer

 

Alright, that leaves me to only two things, is the FMU bad or the Fuel Pump?

Dixit

 

It's got to be the FMU.

Again, considering you're getting 43-45psi at idle with the line removed and 42psi at 7psi, your FMU must not be working.

At least that's what I see.

 

But is it hooked up right? That is the question... I don't know enough about the 5th gen fuel system to be able to answer definitively