88 4.0 no spark to dist

It's been a long time since I've post.
My son in law had to leave his 88 in the mountain. He replaced a ignition module, but still no spark to the distributor. He was asking me, do I think it's the computer? I said I don't know, but I know where to find knowledgeable people that can help. So??? Thanks.

Computer (PCM) is least likely and also hardest to test. Could be crank position sensor, wiring, coil and more. On this forum, the advice is always to test and not just throw parts at the problem. If you have a voltmeter, you can turn the key on and check for 12v at the coil. Also check to see if the distributor rotor turns while cranking.

Note from DJ
Have your son in law book mark this information it is worth its weight in GOLD.

Cruiser54 Mostly Renix Tips can be found here with some photos: Revised on 9-21-2013
http://www.cherokeeforum.com/f51/cruiser54s-mostly-renix-tips-153657/

Most likely suspect is #7-CPS testing and adjusting

A short list of probabilities.

1. CPS. try unplugging it and plugging it back in a few times and see what happens. Do Cruisers test.

2. Power to the ignition module. Check the larger yellow wire to the module with the ignition on. It is usually a volt (or so) less than battery voltage. The smaller yellow wire is the trigger wire and there is really no way to test this reliably without a special tester. Like mentioned it is unlikely to be the ECU.

3: Coil, they don't often go bad, the ignition module even less so. But the connector between the coil and module does mess up and can get way loose with age. Check the module/coil ground.

4. The coil to distributor cap wire can be bad, you usually find that the hard way, by shocking the snit out of yourself. But it can also cause a very weak spark, that can be hard to see.

If he checked the coil to distributor wire for spark disregard, if he tested a spark plug cable for spark, look inside the distributor. Could be a bad rotor or arching inside the cap, most times it is water inside the distributor. Water in the distributor can be hard to see sometimes, it can collect under the cam position sensor mounting pate.

I printed our Crusiers checklist, put it in a waterproof cover and stored a copy in my toolbox.

Note from DJ
Edit to my post #3
Thanks cruiser54 and 8Mud for sharing your knowledge with all of us Renix owners.

Thanks all yaw. It was the CPS

Cox89XJ said:

Thanks all yaw. It was the CPS

Click to expand...

For future reference:



Renix CPS Testing and Adjusting



Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.

Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.

The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.

Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.

You should get a reading of .5 AC volts.

If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.

Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.

A little trick for increasing the output of your CPS is to drill out the upper mounting hole to 3/8” from the stock 5/16”, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.




Revised 01-26-2013