Autozone has the gauge they are better than anybody else for that stuff. I would check the wires that go to your coil .I know it is getting away from the other guys ideas but I had the same thing going on. the other was the module was going off and on.Was running fine then it would act up then it would be fine.
There's a valve on the fuel rail to hook up to. Very very simple, looks like a tire valve, usually right behind the throttle body (is on the 4.0's at least). Gauge should thread onto that valve. Cycle the key (don't start it yet) to prime the pump and make sure there's no leaks @ your gauge connection. Run the gauge line up and stick it under your wiper blade so you can see it while driving. Bring the hood down, careful not to pinch the hose, and latch it up. Go drive and watch the gauge. If it starts to drop, flicker or otherwise isn't steady you have a bad pump.
Your description is almost to the letter of my symptoms. And yes, my pump was bad. If you drop the tank, cut an access hole... you'll be SO glad you did if there's a future problem.
So I hooked it up turned the ignition on without turning on the jeep like it said and it rose slightly to about 5psi. Once started it was idling at 62 psi. Isn't it supposed to be somewhere in the 30's?
Update from the 62psi. Once I started driving it dropped to about the 36 range. Unfortunately I can't get it to not pinch the hose when I shut the hood so I can't see its movement very well. I drove down the freeway for 10 minutes pulled over it was still sitting at 36psi. On the way back it finally started sputtering but the gauge hose was pinched so it wouldn't move. Once I stopped it was still at 34-36 psi and then it started jumping from 32 to 40 psi rather quickly.
This may not be your issue but I would be willing to bet your fuel lines are pinched.
Most likely at the rear crossmember before the fuel tank.
Mine were pinched there and it read a high fuel pressure.
I ran metal lines through the crossmember.
Sorry to tell you this but you are going to have to drop the tank.
Once you fix this issue you should replace the fuel regulator too.
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All the lines I see going to the tank I'm able to slide back and forth a bit so I don't think they are pinched. The readings are weird though. I left it alone for a bit and when I went back out there it was setting at about 32psi. I turn the ignition on hear the pump turn on and it jumps to about 40psi. I start the jeep and it goes back to 60psi. I'm hoping there isn't a pinch as I was leaning towards cutting the floor over dropping the tank if I have to change the pump for sure.
If you are developing the high pressure then the pump is fine. Your return line is pinched. The crossmember has been mentioned. The other possible issue is the rear body mount deteriorate and the body is pinching the line. The last is a possible bad pressure regulator. Not likely if the pressure is correct when you cycle the key on without starting it.
Sounds like I need to spend some more time messing with the return line then. The only thing I don't get if it is a pinched or plugged line is how come it only does it after warming up for 20 minutes, and how come a quick restart allows it go again for awhile?
If you want to make sure its your return line then this what you can do. With the key OFF. Hook up the pressure gauge to the rail. In the pdc remove the fuel pump relay. Jumper pins 30 to 87 in the relay socket. This will turn on the fuel pump with the key off. The pressure should be very close to you reading of 60 that you got with the engine running. Disconnect the middle line from the fuel rail. Connect a hose to that line and put the other end in a gas can. At the fuel pump relay jumper pin 30 to 87 again. If its a bad regulator it will still read high. If it is back to 31 then its a pinched return line.
So I don't have anything to jumper it at my house I would have to go to my dads. I disconnected the return fuel line and tested the pressure upon pumping the ignition it went to 40 psi. I hooked a hose to the return line and turned the vehicle on. Gas started pumping through the hose and the psi was 32. Wouldn't this indicate that the line is blocked somewhere?
We're off topic here guys. The fuel pressure spiking to 62 isn't going to cause a cut-out. And we can't even be sure it's spiking. You may have a regulator or return line issue, but the stalling doesn't seem to be pressure related.
Coils, while difficult to test, are cheap to replace. When was the last time the coil was changed? Coils will break down with heat. The windings within are only seperated by a thin layer of varnish. Varnish will crack over time, and heat causes those cracks to expand, along with the copper wire. Eventually the coils will short on themselves, causing a partial failure and weak spark. Once it cools off, everything returns to normal.
I can't give you a fool proof method to test 'em because it's an intermittent problem. Either swap with a buddy or grab one for good measure.