trovilcl

Hi everyone, so i posted a long time ago about my cherokee not starting. Im in desperate need of some help now. So ok heres the info, the jeep will crank over but wont start. I changed the CPS, cleaned the ground and wires on engine block. Just put in new ignition coil and spark plug wires. i checked all connections and even did a C101 elimination. I have pressure at the fuel rail and the spark plugs are brand new. Im lost. Im thinking about the NSS now and im going to go right now and pull that off and give it a good cleaning. The jeep will only crank over when im in nuetral though. All lights come on on the dash.

DFlintstone

If it's cranking it aint the NSS. In your shoes I'd check spark and see if it fires with a shot of starting fluid. If there is no spark I'd check the CPS. (even if it's new). You might pull a plug after you tried it, and see if it's wet or dry. (a convenient time to check for spark).

>>There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage will in that tube will cause trouble!<<

Cruisers tips are right on top if you click on my signature btw.

trovilcl

yeah i was going to look into the MAP sensor. I checked continuity on the ignition coil, but im starting to doubt the distributer. ill take a look at that stuff ASAP.

DFlintstone

That tube to the map is brittle....the map it's self may well be fine. The tube can break off easily with a piece left stuck in the rubber plug in the TB.

See if you have a nice crisp blue spark....

cruiser54

A Renix will run fine with the distributor unplugged.

Follow Flintstone's advice.

Here:

trovilcl

So im just wondering but how uncommon is it for the ICM to go out?

cruiser54

Pretty uncommon.

Have you checked the throttle body to MAP hose yet as suggested?

trovilcl

No not yet i had to go somewhere today, but ill try to do it tomarrow. Just saying but thanks for all you guy's help.

DFlintstone

You are welcome.

trovilcl

Ok everyone sorry its been sooooooooo long and im bringing back this thread, but i still have a non running jeep. I have done everything so far you guys have said and from what i can tell im not getting any spark. I have fuel pressure in the rail and it cranks and cranks. But no spark. I have already replaced the CPS and the coil. I used Cruisers Renix tips and followed his advice. I took out the C101 connector and verified the Map sensor was good. All the vacuum lines are good as well. I traced the wires around and they are all good. Fuses check good as well. So my thoughts on it is that i think the ICM might be bad. Not sure how to do a test on that though. Any help would be awsome also is there any chat or anything fellow xj(ers) talk at?

trovilcl

ok well i posted that before looking at the old posts. Yes i checked to see if there was spark and there wasnt any. I also replaced the distributer cap and rotor. So heres what i have done so far.

CPS
Distributor Cap and rotor
Plugs and wires
Ignition Coil
C101 elimination
engine ground cleaning and check
MAP sensor check /w vacuum check
new starter
brand new battery
new battery cables
cleaned the NSS
Fuel Filter

DFlintstone

Let's see what others think. I came up with this test with an LED bulb. I bought some lights from the $1 store, but didn't get to testing those LED bulbs. Just an old fashion flashlight bulb may work. If the light blinks, and the coil aint sparking, I suppose that narrows it down. (coil or ICM)
(also you can just go ahead and test that new CPS in about two minutes)

I came up with this test >> An led IS polarity sensitive, it just won't work backwards, won't blow. (12 volts will blow it though)

cruiser54

What's your CPS output?

As for the ICM, I don't know what to tell you except swap a known good one in.

trovilcl

The CPS output if i remember in ohms was like 270-ish it was according to spec. From what i can tell

cruiser54

Here's how to test a CPS properly:



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