Bad FPR?

[bubba966]

Can someone tell me what a bad fuel pressure regulator acts like on an M50TU? Am having fueling issues with one and a fuel pump change didn't fix it.

[whiskychaser]

Can someone tell me what a bad fuel pressure regulator acts like on an M50TU? Am having fueling issues with one and a fuel pump change didn't fix it.
I imagine a bad FPR can give you real **** running or even no start. Dont know the pressure on the M50TU but the M50 is 51 psi +/- 1. With engine off jumper the FP relay and see if you get 51psi. Leave it for 20 mins and see if it drops a lot. It shouldnt. Fire up motor and check fuel pressure. For every inch of mercury vacuum you have, the fuel pressure will go down about half a PSI. A decent motor has about 15-24 inHG vacuum. So if you have say, 18inHG your fuel pressure with the motor running will be about 42psi. Pinch the little vacuum pipe and the pressure should go up to 51. The figures are affected a bit by where you live above sea level but are good to about +1000ft. HTH