Problem with fuel pressure

[PaulRV6]

What would be the likely cause of my fuel pressure changing by 3-4 psi evry so often. I would set it a 43 psi with the vac line off and maybe a few days later or even that same day after driving it would be either up by that much or lower.
It is a fairly new Walbro 340, hot wired with Racetronix kit. The regulator is also fairly new Accufab (alum. billet) I think. I checked the voltage at the back of the car and that seems ok.
What are the likely possibilities? Thanks

paul

 

[PaulRV6]

Geeezz, no relies to this. No one has any ideas on this one? Please

paul

 

[Just a Six??]

You will find that FP changes from a Cold engine to a Hot engine so I set mine when the engine is fully warmed up.

 

[my1stgn]

It could just be when you check it. Your supposed to adjust fuel pressure once the car is warmed up. If you check it when its could it might be a little higher due to the engine running at higher rpms.

 

[PaulRV6]

I don't follow, you check it with the vac line off so it shouldn't matter if it is hot or cold right? the only thing that adjusts the fuel pressure is the vac line, how much vac or press is on the diaphragm?

paul

 

[PaulRV6]

Any others have some thoughts on this? Thank you

paul

 

[vacuum 6]

I check mine only when the engine is warm. Yes you'll get some small differences but nothing to worry about. Check the BLM and O2 #s.

 

[BlackBandit]

I don't follow, you check it with the vac line off so it shouldn't matter if it is hot or cold right? the only thing that adjusts the fuel pressure is the vac line, how much vac or press is on the diaphragm?

paul

Paul, for what it's worth I've experienced this also. The only thing I can think of is that the regulator changes the pressure as it gets warmer (heats up the rubber diaphram, spring, ect.) or the guage reads the same pressure differantly when it gets hot. You're correct. The engine temp shouldn't effect the pressure, but the temp of the measuring/adjusting components might effect the way they work. Just a thought. james