slowpokesi

I think my fmu might be broken, since im running so rich ive come to the conclusion that the fmu is broken, i can take it apart but im not sure what im looking for any ideas?

Curtis2kul

since your running rich? That would most likly mean that its working. If it wasnt working youd be lean

95turboex

first off, what injectors, and ratio fmu are you running, second have you checked to make sure it is hooked up right. If the fuel lines are hooked up backwards it can completely shut off fuel flow with only a couple of pounds of boost, causing an extremely rich problem.

slowpokesi

yeah im beyond all that at this point, everything is hooked up right, i thought that the fmu might be adding fuel at all times, not just under boost ( like its broken)

slowpokesi

f anybody has a fmu laying around that could take a picture of the bottom of the unit thatd help alot, theres a whole in the bottom of mine and i need to know if the mounting bracket is suppose to covr the whole or if its suppose to be open!

95turboex

I had the same problem but it was only really rich until about 4 psi, after that it wasn't too bad. I traced the problem back to a combination of the FMU and the stock fuel pressure regulator. The stock regulator seems to work fine until about 3.5 psi, after that you need the FMU to work. I ended up fixing mine by putting a spring in the FMU to keep extra pressure on the plate so it didn't increase the fuel pressure until after a couple pounds of boost but this takes a little experimenting with pressure before you run the car. I just used my air tank and regulators to tune the FMU before I actually ran it on the car. Just be careful you don't lean out, with boost you want about a 12.5-1 Air to fuel ratio so it will be quite rich compared to you stock A/F.

95turboex

The mounting bracket will cover some holes on the bottom side of the larger part of the FMU. Those are only tapped holes that are used to bolt it together so it doesnt change anything about the way it works.