I found a cause of the Boom! on the Z28. The FMU was stuck! Yep, I did the bike pump test applying even 10 PSI to the boost side, I could not blow through the fuel lines.

Took it apart, noticed the metal diaphram stuck to the fuel part with dried varnish. I cleaned everything with carb cleaner, rubbed silicone lube on the blue silicone parts and put it all back together...works great now.

My question is...that razor-thin half-dollar size silver metal diaphram was also stuck to the blue silicone. Is it supposed to be glued to that? I peeled it off and now it is in place but "loose" with just the 4 allen screws holding it in place, so it can go back and forth with boost pressure..

I began to worry it might get hung up on the screw threads or something. If it was glued in place it would not get hung up...I think.

ANybody been through this?

Thanks, Ram

 

You assembled it correctly, its not supposed to be glued in place.

 

OK man, THANKS!

 

ive heard of the fmu causing big problems. i dont drive my car often and im kinda worried that it might cause my fmu to have this problem sooner than usual. should i take mine apart every once in a while and clean it up to be safe???

thanks

 

ive heard of the fmu causing big problems. i dont drive my car often and im kinda worried that it might cause my fmu to have this problem sooner than usual. should i take mine apart every once in a while and clean it up to be safe???

thanks

 

YES! - That stuck FMU cost me thousands of dollars and a LOT of heartache (for my family too...you know how it can be)

And it is so easy to take it apart and clean. 20 minutes is all.

Maybe this should be a new "Safety", or at least do the bike pump test- you have to take it off anyway to do that...may as well get any varnish off of that fuel port lip and diaphram.

 

alright, i was always scared of taking apart cause i thought id never be able to get it back together.

i sounds like its just a diaphram and a plate....

how do you do the bike pump test?

thanks
jeremy

 

Hey Jeremy...

Sorry so wordy..... Anyone have any corrections? please jump in here.

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FMU bike pump test: (maybe they have it on FAQs, I did not check)

1. Unhook the FMU from the car with those little plastic fuel line disconnector tools you can get at any auto store, drain the fuel out, put it on workbench on paper towels to soak up any fuel and dry off the hose ends. No smoking! Ha Ha!

2. You should not be able to blow through either of the fuel lines. These are on the fuel side (small side) of the FMU. (If you can, it's stuck open- the middle piston is probably varnished stuck to the cylinder in the middle)

3. Hook up a bike pump or an air compressor with a cone type fitting (inflatable toy style) to the Boost/Vac line on the air side (the big side) of the FMU. Give it about 3-4 psi air pressure.

4. Now you should be able to blow through either of the fuel lines...(If not - it's stuck closed... The metal diaphram must be stuck to the fuel inlet tube inside, or the piston is stuck in the middle.)

----------------

Cleaning (whether it's stuck or not...if the car sits, a good idea every 6 months?):

1. Have a clean workbench with enough room. Lay down paper towels.

2. Get a T handled allen wrench to fit the screws.

3. Lay out parts right to left as follows: (below is from memory- anyone -please jump in and make any corrections )

Billet Air outer case. (large side)
Large Air blue silicone membrane.
Large metal disc
Small Steel piston in the middle
Billet Center Casing (with cylinder for piston)
Small Fuel blue silicone membrane
Thin metal diaphram. (This is what stuck to the fuel port, which is part of the smaller side of the case- handle with care!)
Left side Billet fuel cover (with fuel lines on outside and the fuel port on inside)

4. BE CAREFUL with that thin silver metal diaphram when you peel it off the blue silicone...it bends really easily. If you kink it, you could have fuel bypassing it and your FP will be lower at full boost... And we don't like that!

5. Clean all the parts with carb cleaner and paper towels, then lube all the blue silicone with some silicone spray to keep it soft and pliable. Also I sprayed a little teflon spray on the steel piston, figured it couldn't hurt.

6. Remember, the small thin silver metal disc goes against the metal tube port coming in from the Billet Fuel cover side and the smaller blue silicone membrane goes towards the Billet Center casing. The metal disc then "floats" between the 4 allen screws when you reassemble the smaller fuel side cap.

7. Tighten the case just enough to squeeze the silicone gaskets out about 1/16" or more evenly all around the circumferences of both air and fuel sides.

(This is just my opinion....figured I would tighten it a little more than I found it - originally it was only about 1-2mm - but since the gasket is probably still compressed from the first assembly. It didn't seem to hurt anything and I wanted to be sure of no air or fuel leaks!

Take care, Ram

 

Better yet, delete the FMU, get bigger injectors and have the engine dyno tuned

 

And you are 100% right!

I did that with 48 lb. injectors, KB Boost-a-pump, Snow water injection, and a "canned" Vortech LT1 blower tune (until I get my long tubes and get it on the dyno for the real tune) ... Still, I will keep the FMU on until I get it totally tuned on the dyno - just as an additional saftey.

Until someone else can afford to do all that, (the injectors were a lot!) I guess they had better keep an eye on it and make sure that FMU does not stand for F***ed Me Up!

 

hey obe1, did you get that guy from back east to tune for you?

there isnt anyone in bakersfield that can tune our cars.

and yes, they are expensive, thats why im still running the fmu.....

how do you like that snow kit.....which one did you get?

 

Snow Kit :

High quality, easy install. Stage 2 MAP kit with programmable electronic controller for initial and full sprays according to your boost PSI. Got the water level option. You don't need the tank, just use your windsheild washer tank, same stuff anyway.

Got 2 nozzles and 2 lines going to the intake to support 625 HP. They will give you the nozzles you need for your HP.

Seen it spray but have not actually run it on my Z28 yet. (will do it this spring on the dyno tune)

I plan to get another kit for my Nos SS to keep the detonation bugaboos at bay and run strong and cool.

If you are interested, just call to chat, they are easy going...their pricing is low as possible too. (Karen) 719 633 3811. Say hi From Rambo .

 

We got a group together and Jeff Creech flew out from North Carolina to tune our cars. If you can't hook up with a tuner you could talk with Jeff Creech about a mail order tune and then check the results on a dyno with a wideband O2 sensor.

 

Thanks for the info - I'm good. Tuners in St. Louis.. although Creech is closer to me than you! ALso there's Brian Hertzer at PCMSforless.