jumping fuel pressure?

[gnturbo]

Sorry this will be long....Went to reynolds this weekend to get a baseline.Set fuel pressure at 45psi with the thrasher 108 chip.Made my run and came back pulled my vacuum line to check fuel pressure.It was at 40psi?I bumped it up to 45 and shut the car down.Came back a while later after it had cooled down and fired her back up.Line off FP is now at 50psi made a run anyway came back fuel pressure was 45psi line off,exactly 5psi difference.I let the car cool off for a bout 10 minutes ,fired her up ,50psi line off!!!!Where should I leave this fuel pressure with it moving like this and has anybody had this situation?I have a new billet regulator from accufab,Racetronix walbro 340 setup and 868 injectors that are a couple of years old.Don't really know what to point the finger at?HELP,By the way I am not getting any knock after running and finding the fp at 40psi.

 

[BoostedBug]

Is the car running rich at 50lbs? Is it lean at 40 lbs?

I would look into that gauge...Have a friend with one that you could swap with to test?


Did the ET'S fall off or pick up with thte diffrent FP?

 

[gnturbo]

Thisis the deal,I was having a tough time with my lean/rich adjusting of my afpr .I had the regular old rail mounted fp gauge that everyone sells .I would adjust the fp and the needle would not move at all unless I turned it a lot.I bought a metco liquid filled gauge and man what a difference.It is right on and responds with the slightest turn of the allan key unlike the paper generic gauge I just removed.Now I can set the fp and actually know what it is at but I found the flucuating fp after I replaced the gauge.It is a very nice gauge but maybe it is wacky also or I have a gremlin in the car.everything in the fuel system is good quality stuff,The racetronix walbro 340,accufab regulator and the liquid filled gauge.I really don't know if something is getting hot and throws off the gauge or what.When I get through with a run and the gauge reads 40psi,I would not have known it because I did not get any knock or retard.who knows but if anybody has had this happen lemme know what you found it to be.thanks

 

[gnturbo]

No ET change with different fp.
The scanmaster is showing a little lean at WOT(680-730) but no knock

 

[gnturbo]

I will make it simple.I set my fp to 45 when the car is cool,After I make a run or drive the car and get it all warmed up and check it again it will be 5psi less than what I set it at,when the car cools back down and I check it it is right where I left it at 45 psi.When the car warms up am Irunning lean or what .my o2s have been low like 730 at wot but my blms are right around 119-130

 

[gnturbo]

ttt

 

[gnturbo]

no one has ever had a problem with fuel pressure flucuating?,I guess if i posted a question about something like color of plug wires everybody likes I would get more replies.

 

[gnturbo]

ttt

 

[Racetronix]

Either it is the regulator, manifold signal to the regulator, fuel pump or voltage to the fuel pump.

Check your vacuum lines leading to the regulator and make sure they are tight, no cracks, leaks etc...

Put your factory FP regulator back on the car to see if the FP is stable?

Check your fuel tank ground with a digital multimeter. There should be very little potential difference (voltage) between the tank and the frame of the vehicle. Check to make sure the Racetronix fuel tank ground clip is making good contact.

Jack
Racetronix

 

[scottyb]

Jim, pop on a 237 regulator (and adjust boost accrdingly). Run the same cold-hot-cold test and see if the pattern matches with the psi change. This should confirm or rule out the FPR as the cause. I think?