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Need help dealing with a Crank but No Start issue on a 4.0

399 views 1 reply 2 participants last post by  Uniblurb 
#1 ·
First post, so I hope I'm making this right. I have a 96 Grand Cherokee Laredo with the 4.0 engine. A while back when it used to be running, the engine would start and run perfectly until it would randomly shut off. It doesn't even studder or cough, just quickly and quietly shuts off as if I turned off the engine. I would have to wait a while before the engine would start. It got worse until it won't start anymore. Now, my current issue is that my engine would crank perfectly, but won't even fire. When doing the OBDI tests, I got a code 12, 11, and 55. Using an OBDII reader yields intermittent loss of cam or crank signal.

So I replaced both the distributor pickup coil and the crank position sensor, but I still have the same issue. OBDI tests yields the same results, and I don't have the OBD read with me right now. I'm stumped right now since it's my first time dealing with this issue and I'm new to Jeep maintenance. I tried Googling the issue and people said just to replace the CPS and it would run again. I feel like I'm missing something simple, but I just can't figure it out. Any suggestions?
 
#2 ·
Just as a heads-up the key trick isn't referred to as OBDI. It has to do with electronics and OBDI is for the 93-95 while OBDII is for 96-98.

If you installed an aftermarket crank sensor rather than Mopar that very well could be your problem. I bought 2 brand new BWD crank sensors thru Advance and they were just as bad as my bad OE one.

There's a crank sensor resistance test in my signature but the below one is even better in checking for crank sensor signal. This is for a no-start condition only with no-spark. And the coil wire needs disconnected along with the fuel pump relay in the PDC needs pulled.

http://troubleshootmyvehicle.com/jeep/4.0L/how-to-test-the-crank-sensor-1

Do you have the CEL coming on for a few secs when 1st turning the key on? You should if the PCM is communicating correctly.

There's some real good info in the dirty dozen thread in my signature and make sure all your grounds are good/clean. Good luck.
 
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