My fuel pressure when I start up the car is bouncing around from 75-80psi at idle.
It would slowly start to drop until about 50psi where it should be but sometimes while I'm driving, it will go back to 80psi and car will start running really rich obviously. I see this on my wideband and pull over to check the pressure. Car runs fine at 50psi but for some reason it doesn't stay at 50psi.

Stock fuel pump, RC 550cc injectors, twm FPR, marshall liquid filled fuel pressure gauge.
The FPR was adjusted and it lowered the pressure to 50 but it still goes back up.


Anybody have an idea?

 

Bad FPR....Take it apart and reassemble.

 

I'll have a shop do this I guess.
"Do not attempt to dismantle this product. It will be impossible to re-assemble it correctly and will void any warranty."
kinda scares me on their website.

 

Send it in under warranty if you can then. Tell them it doesnt keep constant pressure like it should.

 

Where is your fuel gauge tapped in at? I think stock pressure is like 43 psi and since its a raising rate, at WOT it should be at 55....under stock conditions.

 

It's about 5-6 years old.
I don't think its under any sort of warranty.
I contacted TWM and talked to Garry. He said hes sure its the diaphragm and it's $43 to a new one. So he's gonna have it shipped out to me next week.
Apparently its a very easy fix but I wonder if I can just do what you suggested and just reassemble it for a temporary fix for now.
I'm getting the car tuned tomorrow so It may not be able to be tuned with the fuel pressure going all over.
I did talk to the tuner and he said it shouldn't be a problem but if the fuel pressure is always changing from time to time, there may be a lot of problems tuning.
hmmmm..

 

its on the end of the twm fuel rail.
My tuner set it to 50psi base pressure I believe.