I hate to start a new thread on this because i've read so many others, but i truly think this is a unique situation. I have a 1990 cherokee laredo with 187,000 miles on it. I bought it 3 weeks ago not running, it had no fuel pressure or spark. I was shocked when i looked under the hood and didn't see a fuse panel. Anyway, i have replaced the fuel pump and now it works. However, still no spark. Here's a list of what i have done:

*Checked all the grounds for resistance and cleaned them
*Checked all the fuses.
*Checked the plug wires for resistance
*Checked the coil for voltage and i am getting 10-12 volts while cranking.
*Changed the coil and the ignition module with one from a running cherokee and still no fire.
*Changed the CPS with one from a running cherokee, same thing.
*Tested the pickup stator for fluctuation. It tested good, changed it anyway. Still no spark, so i changed the distributor.
*Tested the cap and rotor for resistance and changed them with ones from a running jeep. Still no spark.

I'd hate to send this thing off to meet it's fate so early in it's life, but i'm out of time and money so if it's not fixed soon then it's being hauled off. Please help???

 

It's got gas right? Just kidding.

Pull a spark plug out and have someone look at it while you turn the engine over see if it's sparking at all just to verify.

The only thing it sounds like to me is the ECM, because you've checked everything else.

 

You mentioned CPS, did you mean crank or cam position sensor ?.....

 

Yep, i checked and replaced both. (The sensor on the bell housing and the sensor in the distributor)

 

Test the CPS...Tip 7.

On a Renix, the stator in the dizzy has NOTHING to do with spark.

See the connector for your CPS?

Is there another one by chance kinda near it?

 

Yea, it goes to a sensor in the intake manifold. By the way i got another computer in the mail for it today. Still no dice.

 

Normal... Rarely the ECU.

What's your CPS output, and is there more than one plug on the harness for the CPS to plug into?

 

Since you already had the pleasure of removing your computer why don't you print out a schematic and verify the correct pins are getting power and ground as they should.

You could also take a test light and verify the injectors are pulsing when you crank it.

I don't know if you tested for spark or not but a super easy way is to just spray starting fluid into the throttle body as you crank it.

I have learned the Renix system is SUPER simple. Chances are you have a blown fusible link or some wiring related issue since it seems you have checked the common things already.

 

Still haven't tested the CPS output.......

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

 

So I test the CPS while it's unplugged... how does it get voltage to send if it's disconnected from its power source? And also i'm waiting until i figure out how to throw the dizzy back in the right way. I went to make timing marks on it after i got it out (stupid, i know) and the shaft turned. I'll test the cps as soon as i figure this out.

 

CPS generates an AC voltage signal.

 

Yea, stupid question. My bad. Anyway, I hooked her up and it generated .5 ac volts. Fluctuated a little bit between .4 ac volts. However, I did take the coil out and clean the points on it and the module, and hooked it back together and it sparked when i cranked it. But when i cranked it again and thereafter, no spark no matter how long I held it.

 

Where are the fusible links at? I've looked and looked but can't find any.

 

CPS unplugged while testing, correct?

 

Not the problem, but here they are.