03 3.7 Basket Case - Crank No Start When Hot

[03KJSadFace]

Hey guys from a new jeep guy.
I just picked up this jeep from my sister after she gave up on getting it repaired.

03 3.7 4x4 libby
123k miles

Ran and drove great for years until it developed an intermittent crank no start condition when hot. Eventually it turned into a consistent crank no start condition when hot and even an intermittent stall and misfire condition once fully warmed up.

Shop looked at it and passed it to the dealership.
Dealership ran a compression test which came back fine and a fuel pressure test. 40 psi when running and claimed it was low recommended fuel pump replacement. I am guessing they didn't do a leakdown test on the fuel system (more on that to come).

All sorts of codes were thrown while the jeep malfunctioned from a lean condition to misfire codes to sensor codes.

They ended up replacing the MAP sensor, crank sensor, 2x coil packs, fuel pump, fuel filter, plugs and one more sensor I'll have to pull that info to add later.

So, I get the jeep, see that the cam sensor hasn't been replaced and the pcv valve has a crack. I replace both and it starts up, runs well even when hot. Only thing I notice is a slight bogging down if I idle for 20 seconds or so then immediately floor it. No misfires just a loss of power for a few seconds until it clears up and the jeep takes off. No issues at speed.

I turn the jeep off and still have a crank no start condition when hot. Rock the key back and forth a few times to prime the fuel system figuring maybe its rapidly losing pressure. Viola!!! Success, starts right up! Every time.

Still has the bogging from any period of idle to immediate full throttle but the starting situation has been presumably pinned down. Fuel system seems to be depressurizing almost immediately upon shutdown. Hadn't confirmed with a guage.

Since the fuel pump which apparently contains the return to tank check valve has already been replaced, I pulled the fuel rail to test the injectors and replace the orings. Once I get the rail removed it starts leaking right side from the crossover pipe joint, the orings in there from being moved have now failed. So that nixes being able to test the injectors till that is repaired. I have a new OEM rail coming in and remanned injectors to go along with it.

So my question is. Aside from leaky injectors, an external leak, and the lower fuel pump module check which has already been replaced, are there any other possibilities for fuel to leak internally in the system causing loss in fuel pressure?

I'm hoping that the loss in pressure was due to a leaking injector or injectors and that that was ALSO causing the idle to WOT bogging while the combustion chamber of the suspect cylinder/s burned their excess fuel off.

Anyone with any suggestions? I'm guessing the cam sensor was also causing problems as well as I've seen some wild symptoms of bad crank and cam sensors in these libbys.

Thanks in advance!

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[wdflr]

Sadface,
I think you are moving in the right direction, replace the bad fuel rail, I would check the injectors, with injector cleaner and some wire, or a donated clip from a junk yard. O rings are easy to change, if the injectors work ok. When everything is put back together, if your still having an issue, I would put a fuel gauge on the fuel line and check the fuel pressure while running, and after shutting it off, Its not impossible to get a bad fuel pump.
I always try to keep it simple, make sure the fuel system is right, then look elsewhere!

 

[03KJSadFace]

Sadface,
I think you are moving in the right direction, replace the bad fuel rail, I would check the injectors, with injector cleaner and some wire, or a donated clip from a junk yard. O rings are easy to change, if the injectors work ok. When everything is put back together, if your still having an issue, I would put a fuel gauge on the fuel line and check the fuel pressure while running, and after shutting it off, Its not impossible to get a bad fuel pump.
I always try to keep it simple, make sure the fuel system is right, then look elsewhere!

Awesome, so the only check in the entire pressurized portion of the fuel system is the one located inside of the lower fuel pump module?

Thanks for the help!

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[wdflr]

To my knowledge, that is correct!
You may be loosing fuel pressure at an o-ring in the fuel system though, you should have an o-ring at the fuel pump, both sides of filter, and I be leave a return line from the filter, to the fuel pump.
Also at the fuel rail.

 

[03KJSadFace]

To my knowledge, that is correct!
You may be loosing fuel pressure at an o-ring in the fuel system though, you should have an o-ring at the fuel pump, both sides of filter, and I be leave a return line from the filter, to the fuel pump.
Also at the fuel rail.

Ok, new rail in. Remanned injectors in. Starts up runs great. Still has a crank no start issue without priming the fuel pump by rocking the key.
I've noticed this:
When I shut the engine off, particularly on an incline, I can HEAR the fuel gurgling as it drains out of the lined and back into the tank. In fact, I can hear it returning back into the tank my putting my head down near the bumper after I shut it off. Sounds as if its returning back from the upper module that attaches to the top of the tank. Reason I say that is I can hear a stream like someone's ******* inside of the tank.

So with that said, what the hell could it be? Fuel pump module (the lower/brick) was replaced by my sisters boyfriend before they gave up on it. Why would the fuel be returning to tank from the tanks top flange?!?!

I guess next step is to pop the service cap ontop of the tank and visually see what its doing once shut off?

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[renegade 04]

Sounds like there could be a bad check valve somewhere in the system.