Fuel PSI question

[camcdaniel1]

1995 Wrangler 4.0 what turns the fuel pump on /off. I realize the rail PSI is controled by a vac reg. When you trun the key on the pump runs till it builds Psi then turns off. My jeep runs for a few minuates then starts to stumble. I can turn the key off and right back on and it runs fine for few minuates then starts to stumble again. Is there a sensor that turns the pump on and off?

 

[GaryMB]

The ECU controls the fuel pump via the ASD relay which in turn controls the fuel pump relay; several sensors give input to the ECU to control this. I would try replacing the fuel filter, and if that doesn't do the trick then hook up a fuel pressure tester to see if the fuel pressure is the problem.

 

[camcdaniel1]

Thanks for the help!! I've replaced the filter already. What should the PSI be at the rail?

 

[camcdaniel1]

Another thing. I removed the vac line to the reg and it made no differance in the driving. Should it be able to run with the vac reg line disconnected?

 

[GaryMB]

PSI should be around 40 I believe. Disconnecting the regulator should actually increase fuel pressure, I would keep it connected to avoid damaging the pump or causing a leak. There is a number of things that could be causing your Jeep to die; what engine codes are you getting from the check engine light? (turn the ignition on-off-on-off-on in under 5 seconds, but NOT all the way to start).