No Start

[warf90]

Please help me diagnose a no start. My MJ is a 1990 with the 4.0. I have checked for spark at the ignition coil and do not have any. Where do I go from here? I do not have a chilton manual or anything. Any help would be greatly appreciated.

 

Thanks

Warf90

[GirsMJ86]

http://www.comancheclub.com/forums/view ... hlight=fpr

 

read that. i helped him out a little bit into that post. most the things i told him can also cause a no start/no spark. if none of those solutions are it then i have a few more i did not tell him since they did not go along with his problem.

 

Alex

[GirsMJ86]

here is one that would go along with your problem a bit better. the CPS (Crank Position Sensor). it is on the bellhousing near the engine at either 11 or 3 o'clock position. if it is not connected or there is a short in the wire your jeep won't run or start. let me know if none of these fix it.

 

Alex

[87manche]

classic CPS failure.

There's a connector with two wires on the firewall, near the map sensor. That's the CPS connector. Unplug and replug it. It's a very weak signal from the sensor, and the smallest bit of corrosion causes problems.

[warf90]

If the crank positioning sensor or connector for the map sensor is bad, how does that effect spark from the coil? Does it kill the 12V to the coil?

 

Thanks

Warf90

[Pete M]

The CPS tells the computer where the engine is in it's rotation and the computer won't fire until it is absolutely positive it knows exactly where the engine is in it's rotation.