I have a 1989 jeep xj 4x4 and have been driving it regularly on the weekends and to town now and again. got in it to leave today and it turns over but won't start. Anyone got any ideas on where to start looking?? I checked the air box to make sure rats hadnt plugged up the breather and that is as far as i have got. gonna push it into the shop and look at it tomorrow. It ran just fine until today, no misses, or anything...just quit....????

 

1. Check for spark. Pull a plug, keep it attached to the plug wire, place the plug electrode near a good engine ground, have a buddy crank the engine while you watch. You are looking for a strong, blue, snapping spark. Yellow/orange/white indicates a weak spark which may not be strong enough to start the engine. Common causes of no-spark on an 87-90 include the crankshaft position sensor (#1) then the ignition coil, then the ignition control module (in THAT order)

2. Spark is good? Then try a small spray of starting fluid into the intake. If the engine starts and runs momentarily, that confirms a FUEL DELIVERY problem.

The above two simple tests will help you narrow this down considerably. Check back and let us know what you find!

 

thank ya sir ..will get er in the shop and check it out....will let you know..

 

im having the same problem with mine, it is getting spark to the ignition coil but not going to the plugs. I cant find the CPS on my 1990

 

Top of the bellhousing.

 

when i test it do i check the cps end of the connector or the other side?

 

89 jeep Cherokee 4x4 straight six 4 lt.
Turns over but won't start ....
It was random at first but now won't start at all...
Replaced: cap rotor plugs and plug wires ignition module & coil
Battery terminals and ground straps are clean...
There is fuel in the rail and my injectors are only two years old at most.
Got spark fuel and oxygen ???
Compression?
Any advise or suggestions would be much appreciated
Thanks, Mike

 

1. Do you have a strong, BLUE, snapping spark? Yellow/white/orange indicates a weak spark which may not be strong enough to start the engine. Check it again to verify.

2. You need approximately 31 psi of fuel pressure to start the engine. Must be tested with a fuel pressure gauge. A fuel pressure gauge can be rented from many parts stores.

 

I know this is an old thread but I could use some help with the same issue. Any advice would be much appreciated. Please help!

1989 Jeep XJ 4.0 I6 died while going through a car wash a week ago so I believe the cause was water related. It will turn over but will not start. Here is what I have tried so far:
- fuel pressure consistent at 40 psi while attempting to start
- replaced CPS (not fun by the way), no change in symptoms
- took distributor apart to allow it to dry
- getting blue spark from ignition coil to distributor
- spark at plugs appears more white or yellow
- when starter fluid is sprayed in the air intake, it will run very rough for a second or two

 

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

 

Would I get spark and fuel if the brand new CPS was bad?

 

No.

How good of a spark? Blue?

Try this. Takes 5 minutes.

Renix Jeep ICU/Coil contact refreshing
　
　




The contacts between the coil and the ICU on your Renix Jeep can become corroded and loose causing a complete or intermittent no-start condition. I recommend the following procedure as a maintenance precaution to insure this is eliminated as a possible cause now and in the future.

The coil is attached to the ICU by two T20 Torx bolts. Remove these two bolts and lift the coil up off the ICU. You will see 2 pins and 2 sets of contacts. Clean both the pins and springy contact pieces with a good electronics cleaner and some fine sandpaper.

Squeeze the springy contacts closer together with some needlenose pliers. Bolt the coil back on to the ICU.

While you’re right there, unplug the connectors from the ICU and inspect the pins in the harness connector. Make sure the pins are not retracted into the connector. Spray out the connector and the receptacle of the ICU with the same good electronics cleaner you used earlier.

I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.

　

Revised 04-04-2013

 

Spark to the distributor is blue but spark at the plug is more white or yellow. I am definitely getting spark and fuel but I failed the CPS voltage test above. You are saying I would not get spark and fuel if it was CPS? I will do the procedure above and I will probably replace the coil and maybe the distributor next.

 

Pull the distributor cap and have a gander in there.

 

Thanks again. I removed the ignition coil, cleaned the contacts, still turns over and won't start. Installed new ignition coil, same symptoms. Two questions:

1) I have the distributor cap off now, what am I looking for or should I just replace it?
2) My CPS does not return measurable voltage but passes the ohms test. Is it possible this new part is my problem even though I do have spark and fuel?