Topic: 1999 tj SE cranks but won't start

[DaveNC]

Happened about a month ago, TJ was idling fine on a downward incline. As it was warming up it just died and would not start. When cranking for a few minutes it would not start and their was a smell of Gas. I assumed I flooded it so rolled it to flat ground and left it until the next day. Came back with a few tools and starter fluid but still cranked but would not start. My assumption since I just gave it a tune up with quality parts (Autolite XP Plugs, new cap and rotor with brass, new wires and NGK ignition coil) was possible the Catalytic Converter (Engine has 140,000). Tow the TJ home and drilled a hole in the exhaust pipe. Took a bit but the TJ started up. I ordered the pacesetter direct fit Cat and yesterday went out to put the TJ up on ramps to get ready to swap out the cat and downpipe (while I have the skid plate off I figured it is a good time to flush the auto trans and change out the trans filter). Again crank and no start. I am perplexed. Is it the Cat? could the Ignition Coil be bad? Maybe the CPS or Cam Sensor is bad? I also already switched out the TPS and cleaned the AIC. Also worth mentioned that the TJ does try to turn over but when the key springs back it stops. Please, if you have any ideas where to start let me know. Thanks.

[DaveNC]

Also, I don't think it is the PCM because when turning the key to start the check engine light illuminates as it should.

[DaveNC]

Also - pulled plugs 2, 3 and 4 which were black and had fuel on them.

[Jeffy]

I'd still check the PCM for codes.  I doubt it's the cat though.  I'd check the spark plug wires and see if you can see them arc if you hold it close to the block.  If each one is arcing then you know the C(am)PS works and the cap and rotor are okay.  What's the gap set at?  0.035" is what it should be IIRC.  The C(rank)PS is the one that's harder to varify.  When they go bad they do weird things and sometimes don't throw a code.  Hard starts or no starts is one of the symptoms.  You might also check he ground strap for the engine.  weird things happen if that's not connected as well.

[DaveNC]

Thanks Jeffy for responding.  I previously cleaned and reinstalled all the ground straps and the vehicle was running good. I just checked spark for plug number 3 and it seems to be sparking intermittently. At first I thought it was a PCM because the check engine light was not Illuminating when I went to go start the vehicle, however it turned out to be a blown bulb. New cat is installed.

[DaveNC]

Checked all the plugs for spark and they are good. Just looks like the Sparks are not at a steady rotation.

[95 Lowbuck]

I would put the original coil back in and try.

[DaveNC]

Lowbuck - I was thinking that too but I dispose of the original Coil about 2 month ago and the TJ was running after I installed it.

[DaveNC]

I was able to borrow a code reader from a friend. P0391 and P1391 are coming up. CAM or Crank positioning sensor? I am not sure.

[DaveNC]

Turned out to be the crankshaft positioning sensor. I threw in a used one that was removed from a running jeep Cherokee. TJ fired right up and codes went away.