fuel pressure reg actin funny

[littlevictories]

So I just swapped intakes, fuel rails, injectors, and FPR on my 2002 DBC flex fuel 5.3. -kept the original return style fuel crossover . the intake and rails are also from a flex fuel truck but DBW.

I was trying to cure a possible vacuum leak.

Now the truck won't prime up to 50psi with the key in run. The pump primes, but the pressure at the rail quickly drops back to zero.

To start it, you have to crank for ~5 sec and then it fires. Before it would fire instantly.

When you shut it off and you can hear it whistle/gurgle down.

I swapped FPR's to the old one, same game. I'm worried that the drivers side rail i swapped in is messed up.

Any ideas on where to look after that?

[ls1nova71]

Did you swap it with all flex fuel parts? The rails and regulator are different between the flex and standard. If your pressure is dropping you are leaking somewhere, could be inside the regulator.

[littlevictories]

well i thought this other motor was a FF motor, has FF type injectors and the FPR is marked ethanol compatible.

I'll swap rails/regulator and see if that fixes it.

[BR3W CITY]

Do you have a vent? Some of the return systems get grumpy if they are trying to flow back into a tank thats semi-pressurized.

Take the gas cap off and see if it does anything different.

[littlevictories]

yep, just fixed that fiasco with a rollover vent and a charcoal canister. i'll double check the vent is working right.

[littlevictories]

doh! had the inner FPR seal pinched!

not sure how I managed to do it TWICE on two separate FPR's, but I did.

Is fixed now. new injectors made the negative LTFT's chill out, must have had a leaky one.