RangerRyan

Cheers all. I've been lurking the forums for many years now, but finally need to cry for help.

Update: fixed - exhaust was clogged at the dent!

2001 XJ 4.0 126k miles is cranking but not starting after I plugged up an exhaust leak. There was a significant leak where the pre-cat joins the mid-pipe. I made a gasket and sealed it up completely. (worthy side note: the mid pipe has always been dented pretty bad after the first bend, constricting the diameter of flow to only about 40%) It now cranks, and after a few seconds will want to start but then backs off and on.

I am currently troubleshooting the basics and testing spark tonight, but do any of you have any idea why it will not start after this exhaust fix? I already reset the computer twice by disconnecting the battery for a full day, etc. Prior codes are now cleared and wont pull. The prior codes were 1. multiple cylinder misfire, 2. evaporate emissions small leak detected, and 3. cylinder 5 misfire. I have an OBII scanner available.

History: She's been running terrible (jerking/dying at hotter temps/lower elevations) assuming due to this exhaust leak and possibly cracked headers. I decided to plug up this leak first to see if it's leaking at the headers (yes I already replaced engine/tranny mounts in case I get new headers).

Thanks a ton for all of your worthy advice! I have to order all parts online since I live in the middle of the forest, so these fixes take some planning =/

NewbJeep

I can't help you diagnose the crank/no start but I can offer some other bits:
The bend in the pipe is supposed to be there. There's some debate but the concensus seems to be for the front driveshaft clearance.
With all those cylinders misfiring and the jerking at high temps, you may want to start looking at the dreaded 0331 head-cracking issue. Just as a free check, how does your oil and coolant look?

RangerRyan

All fluids are good. The only symptom I can think of that I have from a cracked head is a very tiny coolant leak that soaked on one of the 02 sensors on the pre cat (haven't pinpointed it). Never experienced any typical coolant loss.

RangerRyan

I just recreated the exhaust leak and it starts and runs.

I then tightened the joint to seal the leak while it was running and she died. Any suggestions?

dans98xj

Your cats my be clogged. Try tapping them with a hammer and see if you hear any rattling. If you do then the catylist has broken apart and clogged the exhaust flow. It may even have fallen onto the dent in the pipe and clogged it from there. That could be why when sealing it up it dyes out. When the leak is present there is a place for the exhaust to go.

CCKen

RangerRyan,


Can you take a photo of this flange you tighten when it quits and post it here? Is it in the pic below?


Here's a pic of the 2001 exhaust manifold/Cats (prior to the exhaust pipe).


As I recall, the 2001 has an unmonitored down stream CAT (not pictured). I wonder if it's plugged up and when you tighten the system up the back pressure from the downstream Cat is causing it to quit.



,

caged

i too would say plugged cat