89 Renix 4.0 Auto Weird Starting Issue

[chastings]

Current post is regarding my 89 Cherokee but I've been quite pleased with the responses on this board regarding my Comanche so figured I'd post it here.

 

Sometimes when I crank the jeep it cranks a little bit slower than usual (just slightly), the tachometer starts jumping around, there will be a slight cough, the cranking speed slows then it stops cranking completely. I turn the switch off and try again and it usually starts the next try. It doesn't always do this, maybe once every 20 starts or so.

 

The battery is a new napa legend with new cables. I tested the crank sensor a few months ago. It showed .4 ac volts indicating it is weak--also, when I unplug the crank sensor it cranks much faster.

 

Since it tested marginal I think I'll replace the crank sensor and see what happens. But this is such a bizarre sequence of events it seems that I may have another issue that's contributing to my starting issues.

 

When this occurs it seems as if it's trying to fire at the wrong time during the start sequence, throwing off the crank speed. Fwiw it runs fine, no issues other than an occasional hard start

 

Thoughts.....

[cruiser54]

If you're gonna replace the CPS, get a quality one and modify it per post 7 in my Tips.

 

Of my Tips, which have you performed? 

 

I would recommend #1,3, and 4 right out of the chute. 

[chastings]

Thanks cruiser. I've done 1, 3, 4 and 7 over the last 3 years. I did the ground refreshing when this first came to light late last year. I'll probably swing by my local Chrysler dealer and get a cps from them.