Fuel Pressure???

[racin4ds]

Been chasing a fuel system issue in my Cobra for awhile now and after some searching around I've found varying fuel opinions of what my Fuel rail pressure should be. Reading via my Predator I'm getting 39-40psi at idle which seems high?

What do you guys see at idle?

At WOT?

Thinking my FRPS may be faulty causing some of my issues.

 

[bubblehead93]

PCM will work to keep 39# above manifold pressure unless this has been changed in the tune. You should pull 20" of vacuum at idle, equates to about 30# fuel pressure at idle. At WOT it should read boost pressure + 39#. 39-40# at idle is high, something is wrong, could be a bad frost - have you tried unplugging your frps (electrically). Do you datalog?

 

[racin4ds]

Yes I datalog with my predator. Fuel pressure is constant ~39-40 during idle and cruise, peaks in the high 50's low 60's under boost but my pumps are at 100% duty cycle by 4000rpm...

I haven't disconnected the FRPS, didn't know if I should or not, what good will that do?

I'm so damn fed up with this car at the moment.., just got done dropping the tank and replacing the pumps thinking that was my problem and then I found a hole in the line just after the PPRV so replaced all lines and it didn't change a thing.

 

[04CobraMatt]

Your predator is showing correct.

Our cars don't have built-in actual fuel pressure, just "pressure drop across the injectors" which should always read around 39.

Your actual fuel pressure is around 30psi for idle and +1 for each lbs of boost. You'll need to buy an aftermarket fuel pressure gauge to see that.

 

[racin4ds]

If thats just pressure drop across the injectors is it supposed to go up when in boost as well? Whats normal? I'm just trying to rule out some parts here while figuring out my fuel issue and I don't really have the cash right now to just go out and buy parts that aren't bad