So today I installed an electric fuel gauge in the car because I had a mechanical gauge underhood and it doesnt read right. Duh. So then I get it hooked up, and I could have sworn I was running around 20 PSI. Using the adjustable regulator that comes on the HOlley tbi unit.

So it is showing me 10 psi. So I bust out a mechanical gauge I use at the shop, hook it inline with the fuel feed line. front of engine bay, disconnect top hose. This shows me 50 psi. No way the car would run with 50 PSI of pressure, not a TBI engine. So I say has to be wrong, I install a different gauge. 50 PSI. WTF? ( I am running the walbro 255 LPH pump). So at this point I am thinking that thier is someting causing these not to read right.

So I start adjusting the regulator, one way til the car dies. So I back it off and go the opposite way, which it dies because I basically took all pressure off. The electric gauge showed no pressure, but all the way the other way it would only go to about 15 PSI.

Key on engine off the gauge jumps up to 40, then kicks down to 0.

So by this point, the engine is flooded out. I try cranking more and nothing. So I get the engine unflooded. Some other stuff happens like rotor blowing to pieces. etc. lol.

I get the car running again, and adjust the regulator it adjusts to 21 psi which is where I need to run. car is running good no problems. I reinstall air cleaner, clean up a mess on the floor. go to leave, and car wont start. gauge is showing 40 psi, only on key on engine off. Shows nothing otherwise. So I adjust the regulator down more. car is running fine now.

So that is all weird to me!

But my main question is does anybody know if the holley tbi comes with a certain # spring. Meaning it can only be adjusted from this # to that # of pressure and maybe I need a different spring to get the pressure I want? I am thinking it let me adjust, but it would not hold the adjustment because of a weak/or too stiff spring? what do you all think?

And sorry for the long post. I am trying to be as descriptive as possible.

 

The holley regulator and the walbro 255 dont mix well. The regulator has very small return passages, and as such, suffers a lot of drift in fuel pressure. In mine, the fuel pressure would fall from 35 PSI at idle to 20 PSI at WOT. The reason is that there is a large pressure drop thru the regulator at the flowrates that the 255 delivers. Something like 12-15 PSI on the return side after the regulator diaphram.

Solution: run an external regulator and just T off the TBI with no return. This will allow the external regulator to handle all the flow. The only thing you need to keep in mind is that the regulator should be located close to the TBI, and above the unit so it doesnt self-siphon the fuel after shutdown.

 

Man so you really think thier is no other cure than to change the regulator out. I am trying to run a constant 20-21 psi for what I want to do. Maybe it is better if I look into a VAFPR then so I can get the high psi for high rpm and lower psi for lower end. Was really thinking about doing that in the future and just getting it good enough for now. The unit I actually purchased from you Dimented! haha. You gave me a 30# spring, installing that would not help my issue either right?