Nicolai

My 87xj 4.0l 6l. Starter to fail. I replace the crank sensor and the ignition coil. Still no spark. Friends are telling me is the computer. I'm at a stand still anyone got a clue

DFlintstone

I'd still check the CPS. You need a digital meter, even a cheap one will do. I think I remember you being here before, anyway crusiers tips are right ontop in the link in my signature. #5, ground checking is a minim must! Also highly recommended you clean, or eliminate your C-101 connector!

Anyone with an 87 to 90 Renix Jeep has two or three minutes to see that their
CPS is putting out at least .35 AC volts. I don't mean to come off rude, but if you can't connect a meter and turn the key, we may not be much help.
AC voltage CPS test; Small clips on the meter leads really helps. (you need contact with those little pins while it cranks)

Unplug the connector at the back of the manifold with wires going down to the bell-housing/cps. (it's a three wire plug, with only two wires)
Probe the two wires to the cps with the meter set on AC volts. (a 200 scale on mine).
Crank the engine and note the voltage. (jump it if your battery is low)

Mine somehow works with only .3 my wiring/grounds must be pretty spiffy. .5 seems to be a good mark. One article talked of .5 to .8. **Update, it soon failed. I installed Napa #css980 in my 90, that part will work back to 87. You can also check for 200 Ohm's resistance, +/-- 75, but the ACV is what the ECU is using.

RTorrez1

Are you getting fuel pressure? The reason I ask is if you are changed out the CPS with an after market it can still be your problem. After market CPS's are known to be bad right out of the box and if they do work they have a very short life span. And with a bad CPS you will lose both spark and fuel pressure. Check the fuel pressure and if you don't have any. Return the CPS and get an OEM one. Just something to check out.

RTorrez1

DFlintstone, You beat me to it. You made you post as I was writing mine. Saying basically the same thing.

Nicolai

Okay I'll see if I the requirement are met. to be honest cause electrical engineering is my worst problem. I got a 96 wj that likes to blow the computers been stuck for a years looking for the problem.

DFlintstone

Howdy RT. With a bad CPS their will be no injector pulse! Fuel pressure will come up before you even turn the key to start!

Like said Nicolai, just check it. Can be done in the time it takes to tie your shoes!

Nicolai

Check the crank position sensor . in the process replace the coil module. Thanx

DFlintstone

Change the ICM if you like, but I'd test the CPS and at least clean the C-101 first. And do #5.

Nicolai

Will do that tomorrow lol I'm such and idiot I had to Google c101 what's #5

Jeepcrazy5722

If comes after #4 but before #6, it is also 2+3.

But what DFlinstone is talking about is the 5th post in the link that he told you to check out by Cruiser.

DFlintstone

Yep, on top on the link in my sig. here it is> https://www.cherokeeforum.com/f51/cru...x-tips-153657/

It has two deals on the c-101 as well as the sensor ground test, #5.

Nicolai

Thank you this will help a lot

DFlintstone

ALL the crucial stuff goes through that connector. All the sensors, the injectors. both the TCM and ECU grounds as well IIRC. The CPS signal. Best to chop it out and solder them all, but at least clean it!

Jeepcrazy5722

Just cut it and solder it, it was easier than cleaning it. I never soldered before I did mine and it was pretty easy, took me a little longer than some on here but it was my first time so I was probably being overly cautious.

Nicolai

I'll just clean it got contact cleaner and dielectric greases