still having trouble with my 88 xj

[jolly_rogger]

i've had it with this hunk of crap. i don't know what to do. it is beyound my abilities i gues. I have started to hate it with every ounce of my being. I have spent untold hours away from my family working on this thing. I am now out of money and pateince with this. What more can i do ? If i had the cash i would just buy something else and take a sledge to this thing, light it on fire, and pee on the ashes. What am i missing ? I've done just about everything everyone has told me...i guess the next step is to replace replacing the entire wiring harnes, maybe drop the tranny check the flywheel for rust and get another new cps and insall it..... wait i don't have the tools or place to do that so i guess im screwed.

 

[Ecomike]

You say you swapped the HV coil, but did you swap the ICM at the same time????? The ICM is the ignition computer and sits right under the HV coil.

It is time to pull out a volt-ohm multimeter and start checking wires for continuity and voltages. As I recall with the power on, engine off there should be 5 volts on one of the yellow wires leading to the ICM just under HV coil. While cranking that voltage drops out for a split second under a command from the ECU (in another wire) and the voltage drop fires the HV coil.

According to my E-drawing the black wire at the ICM is a ground, check it on ohms scale of your meter, should be less than 1 ohm from there to the battery ground (-) post. There are two yellow wires from the ECU, one looks to be a 12 volt signal that goes through the fuel pump relay first, then to the ICM, the other should be 5 volts IIRC. See if one of them has 12 volts, and make sure the fuel pump is turning on. The green/white wire seems to be the tachometer signal from the ECU which should be based on the CPS signal to the ECU. It should look like an AC signal, low voltage, under 5 volts of some sort. THe CPS signal is just under 1 volt and should show up on an AC meter setting at just under 1 volt AC IIRC.

In summary, your problem must be bad wiring or bad parts from the CPS to the ECU to the ICM, or no power the ECU or ICM (The 88 ECU rarely dies) itself???

There are 2 diagnostic connectors on the passenger side fender well towards the rear where you can monitor the ECU and sensor wire voltages and grounds!!!! Get a copy of the Renix Fuel injection manual it shows which pins to check!!!

 

[jolly_rogger]

thanks. I plan on swaping out my entire wiring harnes as the last owner did some lousy wiring for an alarm and lights....and there is nothing more i hate then someone elses lousy wiring ...i prefer to do my own lousy wiring...lol. Some of the wires seem a little rough to say the least so i think redoing the whole thing to be a much better option then trying to splice and patch. It looks like a big job to replace the entire wiring harnes but at the same time it doesn't look to be that hard. I will start a new thread about this. i am hoping that the wiring harnes from a 90 although slightly diffrent will work the same for a 88.

 

[Ecomike]

thanks. I plan on swaping out my entire wiring harnes as the last owner did some lousy wiring for an alarm and lights....and there is nothing more i hate then someone elses lousy wiring ...i prefer to do my own lousy wiring...lol. Some of the wires seem a little rough to say the least so i think redoing the whole thing to be a much better option then trying to splice and patch. It looks like a big job to replace the entire wiring harnes but at the same time it doesn't look to be that hard. I will start a new thread about this. i am hoping that the wiring harnes from a 90 although slightly diffrent will work the same for a 88.

:shiver:And I thought I was a brave soul! Wish you luck! You may just trade one bad wire for another.

 

[jolly_rogger]

lol. I don't think i have much choice. after closer inspection of some of the wires i have found that there is a number of splices cut wires and wires leading to no where. The last owner or the one before that did one hell of a hack job and hate trying to figure out other peoples hack jobs, at least with my hack job i know what i did...and i prefer virgin wires....lol. i even found that i have an alarm... i knew there was a siren left but i didn't know that everything else was there too. The alarm looks cheap and not the type to have any kill features and its not hooked up to any power sources. just for fun i should hook it up and see what happens....lol. thanks again everyone and i'll keep you all posted, with any luck this will work and i'll be at the next stage of my repairs and mods ....next is my tail lights, a new dash cluster (away with the idiot lights and hello guages and a tach !!!!), finish my stereo/CB/VHF installation, installing my new custom bumpers, and then a lift. thanks again and by all means keep posting ideas as this may not fix things.

 

[broqenjeep]

With the key in the on position you should hear the fuel pump buzzing, fuel pressure should be 40 psi at least. Can't remember how many gallons per minute. Went through 3 Autozone pumps before I got a good one, only lasted 18 months now have a bosch OEM pump $250.

 

[jolly_rogger]

at this moment fuel is not my issue the lack of spark is. i might try another new cps aswell. anyone ever buy a new one that was bad ?

 

[in2fords]

I had a custom mount made for my CPS, it wasnt adjusted correctly and it wouldnt fire, finally got the right adjustment in the CPS and it fired right up.
Did the new one have the same dimensions as the old one? could they have given you one for the wrong year?

 

[jolly_rogger]

i'm going to mod my mount a little to see if that works but if it doesn't then i'll be replacing the entire wiring harness as there is some funky stuff going on in there...lol

 

[TRNDRVR]

at this moment fuel is not my issue the lack of spark is. i might try another new cps aswell. anyone ever buy a new one that was bad ?

There is a factory fix for the CPS. It's basically a new CPS plug that you drill a hole into the firewall around the steering column and run the wires directly to the ECU therefore completely bypassing the factory CPS wiring harness. It's a bitch to install, but worth the time ruling it out as the problem. Your Jeep parts counter guy should know what it is. Comes with a new CPS and the new CPS plug wiring harness. About in the $80.00 range.

HTH

Dan.

 

[Ecomike]

Do you know what years it covered?

The CPS changed in 1991 IIRC.

There is a factory fix for the CPS. It's basically a new CPS plug that you drill a hole into the firewall around the steering column and run the wires directly to the ECU therefore completely bypassing the factory CPS wiring harness. It's a bitch to install, but worth the time ruling it out as the problem. Your Jeep parts counter guy should know what it is. Comes with a new CPS and the new CPS plug wiring harness. About in the $80.00 range.

HTH

Dan.

 

[xjtrailrider]

Have you checked the harness side of the connector, it may not be conductive. You could test it easily by placing one test lead on the pin and then probe into the wire just behind the connector with a ohmmeter or continuity tester.

 

[Ecomike]

Opps.

 

[TRNDRVR]

Do you know what years it covered?

The CPS changed in 1991 IIRC.

Subject: Crankshaft position (CKP) sensor and harness replacement on 1987–90 Jeep vehicles with the 4.0L engine

Symptom: No start, cranks okay

Source: Chrysler service bulletin 18-51-88

Here's a link that I got from here.

Again, HTH

Dan.