I bought an fmu off a member on here its an ATI procharger adjustable unit well I think it is it has a bleeder up top to open all the way or close it I tried both positions...I only see a slight change in fuel pressure the car is still running lean in boost I thought this should at least put fuel pressure to like 80 psi its only going to like 50 psi...I have a walbro high flow 255 lph fuel pump and a south bay adjustable regulator I set the fuel pressure to 40 psi and like I said in boost with the FMUY hooked up I see 50 total...wow that isn't good im wondering if the FMU is no good or the Rate is too low,,meaning like a 1.1 or something like 2.1...I thought I should at least have an 8.1 ratio FMU...any help would be great please thanks!!!!

 

I also read itneeds its own vac source on the intake were is a good source to use??? I don't see anything that is not being shared...everything is tied together any idea where else I can run the vac source too????

 

Your only guessing.
You need your car on a dyno being datalogged and tuned so you can see exactly what your fueling is and if you have enough when it goes into boost.
You can't just say " it should have 80psi "

 

The the car a fuel pressure gauge in front of my eyes and a wideband also in front of me...so when in boost the fuel pressure does not ramp up wide band shows lean between 15-16 if im seeing this with my eyes I know and im not guessing it should be 80 psi ,,because it is not going up in fuel pressure that's why I asked how can I tell if the FMU is not working....I know it has a decent vac source and it is ramping slighty but not the rate it should be...The car is not going to get a tune for that's why Im trying to use the FMU to at least get it richer in boost....the car has a brand new 2 week old high pressure walbro in tank 255 lph so im sure that can keep up with the fuel demand....I know the FMU is the best way but it should work for now...and at least ramp up the fuel pressure so the car will run richer....

 

the fmu raises fuel pressure at 12:1 or thereabouts under boost, not 1:1. This adds extra fueling. The **** on top is an adjustable bleed, open it more and it will reduce the pressure step up. One thing though, there should also be a small white restriction pill thingie in the line to the FMU.

 

Ok I have the valve closed all the way...the restriction pill thing what does this do? DO you know what it looks like I don't think I have it came with it I did buy this second hand...would this make it not work right not having the restriction pill?...can these be rebuilt if the diaphram is broke?..im wondering if its not 100% any way of testing it?

 

ok went to go check the pill is in there...Its in the white plastic connector that goes to the vac line source...Also they say to hook it up to a vac source al by its self I cant find one so I tee it in the FP regulator...

 

this is it, it restricts the vacuum signal to the fmu and per ati instructions it is required for proper fmu operation

 

If your saying this is like a 1.5 rate then maybe it is working..i had a base fp of 40 in boost it went to like 50...then this isn't going to cut it for me...I need at least a 8.1 fmu or should I raise the base FP to say 52-55 then it would be like 62-65 in boost??? think that would work..???

 

ok I have the red FMU and the same looking vac line I do not have that Blue thing in the intake pipe...lol...were is the restrictor in this pic????

 

that meant to say 12:1 (that's maxsetting can be regulated down to 1:1). so much for auto correct.
The restrictor is there so the air bleed even has a chance of working. It's the white thing in the rubber line. Without it it's way too small a bleed and adjusting it will do nothing.

The blue thing is a custom blow off valve.

 

Well if all that does is bleed off the extra pressure, closing it off would make it go to full 12-1 ratio even with out the restricting fitting. To make the adjustable part work it wouldn't be hard to fab something up if you can find out the hold size. Still you have the problem of it not giving a 12-1 ratio you need to figure out, maybe open it up and have a look.

 

Yesh the restrictor is there and there is no way its going to 12.1 the fuel pressure went up maybe 10 psi...im thinking a faulty FMU its ramping more like a 1.1 then a 12.1...I think im just going to buy a brand new vortech 8.1 fixed ratio FMU...the only thing that bothers me is it says to use a separate vac source well I don't see one I can use so I Teed it off the FP regulator im wondering if that is having something to do with it...Isnt there a vac source on the lower intake somewhere I can tap into...the lower place I saw was were the FP regulator is.....

 

How much boost? fo you have the feed and return hooked up correct?

 

We have about 7 psi..I was seeing 5 PSI tho when I let off....maybe more never got it that high...because it runs lean..lol im almost 100% I have it hooked up right the side of the FMU line goes to rail the bottom line goes to the return I took the connection off by the blower near the left valve cover and the fitting that came with the FMU only went on one way....do I have it hooked up wrong??? Were is a good VAC source maybe that's it?

 

it needs full manifold vacuum and not T-ed off something else.

side is in, bottom is out.

 

Ok I think the FMU is hooked up right were xan I hook the vac line up to then???? I have no idea were manifold vac is unless I tee it somewhere.can you help me find a place this can go then maybe thats why it isnt working.

 

anything on the plenum is full vacuum, only the bottom small port on the throttle body is timed.

 

ok have it T'd to the FP someone said try putting the T in by the Map sensor should that work???...I have a boost gauge I see boost and Vac I have that hooked to one of the lines coming off the Plenum...so I know that's working,.,,Im just wondering can it just be a bad FMU?....

 

If I take the FMU apart would I be able to tell if the diaphragm is no good???? like ripped or torn..im sure that would make it no work right?

 

do not T anything into the MAP, EVER and certainly not a controlled bleed like the FMU. Remove the HVAC controls/cruise vac line and hook it up to that port to test.

 

Ok I can try that I took the FMU apart and the disc on the bottom that closes off the return line seems worn and the little the plunger on top didn't seem to move it to well...do they still make rebuild kits for these???? Also with a 255 lph walbro in tank do you think that's enough fuel to support a stock motor with boost??

 

Ok I Put the vac line to that spot I saw the Fuel pressure gauge go to about 60/65 Once that's it I think the FMU is shot like I said I took it apart and the bottom diaphragm seems weak like no plunger action I swear yesterday it worked once too so does Procharger make a rebuild kit for these...and if that's a good spot to T it too what do I do about the cruise and HVAC vac lines...lol...Or should I just buy a new vortech 8.1 fixed one and call it a day????

 

I ordered a rebuilt kit for the FMU i think its shot and needs a rebuld i took it apart last nite the bottom gasket looked worn and flimsy i put it back together took it for a ride got into boost saw 60/65 psi on the fuel Pressure gauge ONCE never spiked again...im thinking its worn or or leaking or something....