Hey all, my vortech FMU was working great for a couple weeks but now it seems to be sticking rich sometimes. For example at highway speeds it will stick rich and I'll be cruising and my AFR will be like 10's...

I've heard of the plunger sticking after googling but can't find any answers on how to fix it. I took it apart and cleaned everything with carb cleaner but its still sticking.

Tomorrow I'm going to throw a bit of oil on the plunger and see if that helps....

Anybody ever have this problem and found a solution?

 

So, I've tried a bunch of things to get this to work right and still no dice. As far as I can tell its simply that the fuel pressure doesn't have enough jam on its own to push the plunger back up to allow more fuel through thus dropping the pressure and needs the extra vacuum assist. Because it works fine during normal driving and cruising at low speeds... its only at higher speeds in 4th or 5th when you are at 3k rpm or more it will eventually drop the plunger and over fuel.

I've tried:
Cleaning the plunger and assembly.
lubing the plunger with WD40
lubing the plunger with sewing machine oil
using 1000 grit sand paper and sanding the plunger and where it slides a bunch and cleaning.

So all of these have left me at the same point.

I just thought I'd post this up incase anyone searches for this in the future looking for an answer.

If I find one I will post but I'm thinking I will just live with this till megasquirt comes back...

 

The vortech should be closed at crusing speeds, as you're not in boost. I believe, especially since your fiddling with it hasn't helped, that your problem lies else where. I forget, is there a spring in there to keep it closed when it's not seeing boost? Or keep it open? I forget how it works.

Also, a picture is really helpful, can you take one of that side of the engine bay to show us the routing?

 

Well I believe it works by the fuel pressure keeping the piston up during any running operation other then boost at which point the pressure pushes the piston down slowly shutting of the fuel return thus raising the pressure.

I have the routing correct and I have swapped it out and it made little to no difference.
It just seems like the piston is being pushed down in vacuum. Very strange.
For example again, I'd be driving at 100kms/hr in 5th just cruising and the AFR would be 13.5 then all of a sudden it just drops to 10.0 or 9's ish and then stays around there...

 

Hmm, can't seem to fix all but one of your images.

First of all, mount it properly. Buy some fuel injection hose at NAPA, Shucks, O'rilley's, autozone, etc., and replace all the stock stuff. Use proper vacuum line too. RHD?

 

Dang it... thought I had those dang images the first time. Anyway...

Its mounted ok. For now anyway... I have it bolted down in the only good spot I really have available. It is a RHD car. Its only temporary as I wait for Brain to fix my megasquirt. One of the hoses is new and the other is the stock hose with the protection around it that I will reconnect once MS is back...

I'm just really quite pickled as to why it doesn't work... It seems insanely simple yet isn't working. The only thing I can think of is the piston is falling down shutting off the pump return... I wonder if the fuel pressure going through it is simply not strong enough to push the piston back up and allow flow during less vacuum. IE higher cruising speeds.