I have searched the search bar with no luck. Have a customer with a 03 4.0 wj. 3 weeks ago had a no start condition narrowed it to the cam sensor. Replaced it and all was fine. Last night I get a phone call and he drove 5 min home after work all was fine. Hour later goes out to start and no start. An hour after that he says it starts but runs like ****. I'm like ok crank sensor. Go this morning to pick it up and starts up but runs a little rough for a few seconds then is fine and I drive it to shop no problems. Go out at 10 to bring it in and fires right up. Pull codes and only the p0320 code. No engine light starts and runs fine hot or cold. Now I'm testing the wires for the crank sensor and I'm getting 5 volts like I should but when I check for ohms on the middle terminal it should read zero and I'm getting about 16 ohms. Why the hell does this thing work fine 99 percent of the time and where would the black ground for the crank sensor wires run to? Sorry for the long post.

 

I have heard, but have not experienced myself, that non Mopar sensors are about 50/50 good out of the box.

That being said, I replaced an ignition module on a different vehicle 7 times with an OEM (Motorcraft) part. 7 times. Imagine how frustrating that was as I'm diagnosing it and every time it points to a bad ignition module, but each time I change it out it still won't run.

Anyway, it's been said enough so it could be true. Mopar parts (supposedly) have no substitute.

 

I think I've narrowed it down to a broken ground in the harness. With it running I can move the harness and make it stumble and also quit. I'll let ya know what I find

 

You might have better luck in the WJ section then. I know on the XJ it's fairly common to have a break in the wiring harness by the rear of the head. Not sure about the WJ though.

 

Yeah its roughly in that area. I cleared the code ran it and then when I found the wire(s) I was able to make it throw 2 codes. And make it run like crap and quit.

 

How are the motor mounts? That can contribute to the wire flexing and chaffing, leading to breakage or shorting over time.

 

Wiggled them and nothing. Cleaned the crap out of them anyhow. Sanded the block too.

 

Sanding ground points is great, but have you ever used a piloted bonding brush? They're great to keep in the toolbox.

It's probably just cracked wires though.

 

I was referring to the actual rubber mounts that hold the engine in place. When I find fatigued or chaffed wiring in the wiring harness where it crosses from the engine to the firewall, the motor mounts often typically also bad which causes excessive flexing of the wiring harness.

 

Man I'm at a loss with this thing. Moved most of the harness out of the way. Probed and checked wires and none seem broken with the multi meter. But yet now when I hooked it back there is no start. Yesterday when it was running I literally could just barely touch the 3 wires for the crank sensor and it would stall or try to.

 

I had a similar issue with the #3 fuel injector. Sometimes I had 6 cyl, sometimes 5. Moving the harness alongside the vc would sometimes "fix" it. It seemed that every time I probed the wires, they showed continuity. Eventually, I had enough and changed out all of the FI connectors and ran new wires almost all the way back to the junction. One thing I noted was all of the grounds were spliced together with a very bad solder joint. I fixed that too and have enjoyed have all 6 again.

Stay with it and as suggested, check in the WJ forum.

 

Well after having lunch and calming down a little I started with my multi on the black center wire. Says it should be zero ohms and I'm getting alot. Started pinching and watching my meter was able to get to zero in a certain spot. So I'm just gonna run over it for now and see what happens. Now I'm under a ram 1500 soooo

 

Whelp I got er. Ended up having a couple broken wires. The orange power wires that come from the harness and go to the the crank sensor and cam sensor were broken. And the black with blue tracer for ground to the crank sensor was broken at the plug on the harness side. Thanks for all yalls help. Greatly appreciated