I bought the fmu off of ebay used and took it apart to check all the seals and such. Everything looks good no cracks or tears in the rubber. Below is a pic of it taken apart. Do you think I need the rebuild kit or will I be okay. Am I missing any pieces.
Should I put a check valve on this thing ?
Also it came with this braided steel line... Is there any use for that. The one end has a crazy fitting. I have a couple of the solid lines pictured below (different bends), are thoes gonna be ok to use or should I get braided lines?
those lines should be fine ,you really don't need braided lines for fuel
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I only have one of the barbed fittings. Should the source vac line be connected on the red line, the blue line or on the hamster? Is it ok for the fmu to see vac? Or should I put a check valve on both the red and blue lines.
i would try putting the vacuum feed on the hamster first..if that dont work then use the following directions....
Im gonna explain how the new ones (#2025) work becuase alot of people on this .org site seems to think these work differently..or i should say alot of people think these can work as a FPR also for idle which is totally false.
The one you got looks like a older model which should work the same..its got all the same fittings on it ect; Anyhow your vacuum feed should goto the barb with the red line on it in your picture. The blue line looks like it doesnt have a barbed end on it...which on the newer one's..they do. That barbed that is on the needle valve (blue line) should bleed off vacuum, thats where the check valve will go. The needle valve is the adj. part obviosly..clock wise/tighter= more PSI of fuel per PSI of boost.
Now theres one more adjustment that alot of people think is a base idle pressure. For the #2025 which is for aftermarket boost applications which most of us use or are using (there are different modles for non boost..or OEM boosted cars) theres the on-set screw adjustment ...which is the big screw adjustment in the middle...should have a hex indent so you can use a alan wrench for it..in your picture above it has the nut on it with the washer. What that does is raise's the fuel PSI at atmospheric level...a turbocharge on a N/A car will reach 0 level or atmospheric faster then it would w/o it becuase of air the turbo pumps out while reving through gears..ther-for on some cars (not so much with OBD II ECU's) the computer thinks its running lets say ..-15-10 vacuum but with the turbo its already at 0 level 1 PSI maybe therfor will cuase a lean area. Now how to set this youll definetly need a fuel pressure guage tapped in your line and you figure out what your WOT fuel pressure is...usually around 10 more PSI then your idle. I go a tad higher just untill you can test on a wideband to correct it...so lets say your running 45 PSI of fuel on your cav at idle... and your approximately at 55-60 PSI at WOT..what you do is take the vacuum feed OFF your FMU and watch the guage..(so now your FMU is actually reading 0 level same as atmospheric) and basicly tighten (raise PSI) or loosen (lower PSI) that on-set screw with a alan wrench to the desired PSI of fuel..which in our case would be around 55-60 PSI maybe 60 to be safe..then plug the vacuum line back into it and the fuel pressure should drop back down to idle pressure (45 PSI).
Now when you drive and get on it..the FMU basicly takes over around 0 level so no lean spot regardless where your fuel pressure is on your stock regulator. Hope that helps and doesnt confuse's anyone.....
Thanks for typing all that out man. It didnt come with instructions so you just helped me a ton. I was just gonna wing it with my wideband and fuel gauge on my rail. But now I got a good starting point.
How important is the check valve on the "blue line"?
Two functions are accomplished by the check valve. One, the simple plugging of a small vacuum/boost leak. Second, vacuum is required to pull the preload spring under the center screw away from the valve so stock fuel pressures can be achieved under manifold vacuum conditions.
This allows venting the boost signal to atmosphere in order to adjust the rate of gain, while maintaining a seal under vacuum conditions.
So the check vavle should be positioned so it lets air out but not in correct?
correct...if you have the actual check valve it says to have the white end of the checkvalve connected to the vacuum line that go's into the blue line on his picture..so its FMU barbed end attached to the vacuum line that goe's to the white end of the check-valve and the black end bleeds it to the atmosphere.
at the hamster.
anyways, got a ? ; on my car i have the 255 walbro pump, cartech FMU and the stock injectors/ fpr. MY base fuel pressure is about 50PSI / 60psi with the vaccum line off. I tried to adjust the big allen/nut screw and nothing happened? Can U enlighten me on that? I havent really monkey'd with it much to see if when i crank down on the big allen screw if it raise's the fuel pressure. But for now i have it all the way up and it wont go under 50psi at idle with the vaccum line hooked up . Nother thing i am thinking it might be higher pressure due to the Fuel pump.
thanks
I can lower base fuel pressure down to 22 psi atleast, I haven't went lower than that.
Jake-
The FMU can only lower the pressure to the lowest setting you have the FPR on, the stock one is like 45 PSI at idle with the vac hooked up, so thats as low as its going to go. If you put the adjustable FPR on, you can go all the way down to 30ish.
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ya that is what i figured. Thing too is the Fpr i have on the car now always read higher(i think it is a 2k2 one) then all the other stock ones i had on the rail over the years. (i have a guage on the fuel rail).
thanks
when you test the on set screw (allen nut) you need to keep your stock FPR plugged into vacuum and your FMU...the pressure should read 50 PSI base fuel pressure like you said above...and ONLY UNPLUG the FMU (keep your FPR still seeing vacuum) and tighten the allen head till it reads about 62-65 ish to be on the safe side..then plug it back in. Hope that helps
