So the weather got warmer here in Michigan. A couple times in the last week I turned off the motor went into the house/store came back out and it would start but run horribly. I couldn't get it to clear out, and the motor eventually stalled. Got my fuel pressure tester. When I plugged it in, the system was pressurized to 20 psi and wouldn't start. I bled the pressure off in the line. The jeep then started right up. The pressure gauge then was bouncing right around 30 psi. Any ideas? I've thought fuel pump, heat soak, ignition issues, etc. The needle on my fuel pressure gauge was bouncing while the jeep idled. Stayed right on 30, but it was bouncing a few psi below and above 30.

This only seems to do this when it is warm.
btw jeep is a 1996 with a 4.0 and 110k miles.

 

You should verify this spec, but I believe the 96 has a fuel pressure spec of 49 psi, plus or minus 5 psi.

If that is true, you need to install a new fuel pump assembly as you are way low on fuel pressure spec.

 

Any verification on these specs?

 

mine did that too today and last week cmuman. havnt checked into it yet though.

 

I did find this. Pretty sure the pressure'(s), are 8-10 lbs less, idling with the regulator operating. (they are the MAX, wot #'s)
http://www.jeep4.0performance.4mg.com/tech_specs.html

 

30 is too low. IIRC 42 is minimum with the vac hose on the fuel pressure regulator connected and 49 with it disconnected.

 

Where is the vacuum hose for the regulator? Just want to investigate that more

 

Right on the fuel pressure regulator at the fuel rail. When you pull that hose off, make sure there's no gas in there.