I have a 90 xj 4wd that doesn't crank. Someone went through the harness before I got it and stole some parts off of it, we replaced the missing connectors and parts, but can't seem to get it running. We have fuel pressure, but the issue is no spark. We have replaced the icm with a brand new one, along with the ecu, with no success. The ckp connector is hard wired currently and the ac voltage is anywhere from 3.8-4.6v with 250 ohms resistance. Coil is 2 years old from old owner and they said it has 0 miles on it. Crank sensor is newer. Ground on the dipstick has been cleaned, and still no spark!

The issue I think is that we are getting 3.3v DC on the pcm side of the crank sensor wiring. Both wires have 3.3v KOEO and drop to 0 KOER. There is no 5v reference on the yellow wire going to the icm so no signal.

 

Is your camshaft position sensor im the distributor working. Should read alternating voltage to the coil when cranked

 

I haven't tried that yet, but I was told that the cam sensor only controls the injector fire, and doesn't affect the icm or coil at all.

 

Whoever told you that needs to check a wiring diagram. Cam position sensor has wiring direct to the coil

 

I'm currently looking at a diagram, and there isn't a cam sensor. It's called a sync sensor and the only wires coming from it go to ground, and the other 2 wires go to the ecu. If input to the ecu can affect that, then I'm all for that, but don't want to keep replacing parts that don't need replaced.

All the parts that are new, are the ecu, icm, coil, crank sensor, and crank pigtail.

 

Well, suit yourself

 

You're talking about the renix style xj right? The diagram I have in front of me right now doesn't even show the coil on the diagram because the coil bolts directly to the top of the icm.

 

Whether it is wired to the coil or bolted to the coil ICM, there is a sensor in the distributor that controls when the spark plugs fire. If not, they would be firing constantly and timing would be impossible. The point is, check that sensor

 

Checked the wiring diagram, and the sync sensor only controls the injectors. The ecu sends signal to the icm for spark, but we put a new distributor with new sync sensor in it as well. Checked the sync sensor on a volt meter and it works like it should.

 

You are correct. It's a sync sensor for the injectors.

I'm moving this thread to the correct forum and suggesting you go to www.cruiser54.com and peruse the Tips there. I am also subscribing....

 

Just tagging in.


WOW PETE! WHAT? THIS IS NOT Stock XJ Teck? Where are you moving it to?

 

It WAS in Grand Cherokee Tech. I moved it here.

 

CPS generates an AC VOLTAGE signal. CRUISER'S MOSTLY RENIX TIPS

RENIX CPS TESTING AND ADJUSTING

OCTOBER 30, 2015 SALAD 88 COMMENTS EDIT



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 itself as shown in Figure 2 as Connector A, 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.

Another little tip to save tons of aggravation is to stick a bit of electrical tape to your 11mm socket and then shove the bolt in after it. This reduces the chances of dropping that special bolt into the bell housing.

Revised 8/8/2016

 

A progress update, bunch of new parts, b+ power latch relay works 100% and jumped the relay contacts to test for issues there, we have power on the 2 pins 7&8 to the ecu, ground on pins 11&12 (both on side b) unplugged the front o2 sensor for a rem2 check engine light code. Still crank no spark with no output on the yellow signal wire to the icm.

We have cleaned all grounds that I can find, new crank pigtail because it was stolen, new crank sensor that puts 0.68-0.73v ac to the ecu plug, new battery, all wires have good continuity that should.

Any more suggestions are welcome, about to sell this damn thing.
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