It's so simple - if you suspect it's a fuel issue - START BY MEASURING FUEL PRESSURE! Anything else is just chasing your tail.

If you suspect plugged exhaust - cat, muffler, pipes etc - use a vacuum gauge on intake manifold.

Those things only take seconds to use.

If you suspect spark - pull off a plug wire AT THE PLUG - look at the color of the spark, it should be a crisp thin blue spark. Red or yellow is a weak spark - coil wire or coil.

Back to basics! Sensors are the last thing to suspect.

Why make it so complicated?

 

Well imma do that grounding deal tomorrow because the worst it will do is get a little more juice flowing through my amp. But I was testing my CPS with dc not ac, that might be my problem. And I don't think it's an exhaust blockage because with everything from the cat back taken off it doesnt help, plus it only happens when it's warm. And I replaced my distributer, cap, and plug wires with my bros and it didn't help. If the grounding doesnt Helpand nothing else comes along to test I'm going to swap ALL sensors with my bros. If that doesn't help I'm just gonna say f**k it and swap the motors, fuel system, and electronics over. It's got 100k less miles and it's a 1990 renix (yes his Cherokee had a newer motor swapped in) and yes imma do all that work instead of just taking his Cherokee because my body and interior are in showroom shape...unlike his bondo'd up rig. I'd rather be the person to beat up the rig instead of owning an already beat up one.

 

And my fuel pressure is a little hi at 38psi instead of 31psi but it's backfiring through the intake (lean mixture) AND the exhaust (rich mixture)... Oh and I replaced my injectors with my bros brand new bosh ones and I put his heat shield in. And the distributer is timed and the firing order is correct. I pulled a spark plug the other day and grounded it and I saw a redish/orange spark but didn't see what the spark was like with just the wire and no plug. But all that was with my old distributer not my new one, I havnt tested that yet but it still runs like poop when warm.

 

I'd see what the other guys have to say about the incorrect fuel pressure. I think it matters. I think 39 is what you get with the vacuum line of the regulator. I just went and got this on the CPS, (sory if it's already here!) but he has another on the ICU_Coil...that spark should be blue, ...


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 it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
　
Revised 11-29-2011










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.
Squeeze the springy contacts closer together with some needlenose pliers. Apply some dielectric grease to the contacts and 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. Apply dielectric grease to the connectors and plug them back in.
I feel this procedure should be performed at least once in the lifetime of a Renix Jeep.
　
Revised 11-29-2011

 

??I can't help but be curious. There is no timing adjustment, the dizy does not turn, would hardly matter if it did. ??

 

Well by timed I mean the shaft on the dist is set were it is supposed to, it's not like completely off. And I'll test my CPS tomorrow. The one on my renix now is actually the one off my bros ( which is a manual) cuz I thought mine was bad but it was just a bad coil so I swapped my coil out but didn't swap the CPS back. It could be dirty because it was from my bros stick shift. But it ran great with that sensor up until recently when it started having this problem. I'll try that coil cleaning, grounding, and testing my CPS tomorrow after school and let you guys know. I really apreciate all the help. Btw I'm just using my 91 ford idi diesel until I can get my jeep running but the problem is the forward clutch in the auto tranny is going out on it and it gets 10mph so I really need my fairly fuel efficient cherokee back that has no problems (when running right).

 

The red/orange spark is insufficient voltage to fire the plug properly. Your symptoms exactly! It should be a snappy crisp thin blue spark that will jump 1/2' or more.

Loose coil wire, bad coil wire, or bad coil. Avoid aftermarket coils, they generally are weak to start with and fail early. The "trick" performance coils are even worse!

Get it at the dealer.

It doesn't even have to be bolted in to test it - just put the connector and coil wire on.

 

How much is a new coil gonna cost at the dealer? Because I'm broke at the moment until I get paid but on the other hand I can't keep driving my f350 that gets terrible gas milage. And I'll checkwhat my spark is like with the new distributer today. Should I check that with the plug Connected to the wire or just the wire.

 

well i found out i have an 88 cheroke that should be a renix right? no, i and my bro have a benix computer and the coil i took off my bros was a bendix but my original coil was a renix. WTF?! this makes no sense, are they the same company or somthing? oh and with the new distributer im getting a healthy blue spark wen cold so now i have to see what the spark is gonna be like when the engine is warm. ill tell you guys how its going.

 

Renix is a joint venture of RENault and bendIX. You're fine.

 

mkay. i had alazy day so i didnt even touch my jeep besides check the conition of the spark today. i didnt even check the spark when it was acting up yet, just when it was cold. tomorrow is the day to bust ***** on her and get to the root of the problem.

 

In for answers. I'm pullin' for ya, I hope you figure it out!

 

ok this absolutyl has to be done by the end of the weekend, because guess what! my clutch finally took a ***** on my ford. so i am completly vehicleless until i get my jeep running right. or i get the 04 kia spectra fixed that i have....if anyone has any answers to why my spectra doesnt have any spark id greatly apreciate it. ive replaced the coil packs and the wires, and the crank sensor. im thinking its in the coputer because it has power going to the coils but not coming out and we already tested for faulty coils and they work perfectly. completly off topic but ANYTHING helps at this point. THANKS!!!

 

ok so i just tested my cps just now with it unglugged from the harness and it wasnt even registering ANY ac volts when i was cranking the motor and i used 2 different multi meters just to make sure. but then i plugged it back in and back probed the wires and it read .8 volts at idle and the voltage would go up with the rpm's. was this reading a signal from the crank sensor or the computer? would a faulty cps cause this issue i have only once my jeep warms up? and should i just swap my cps just in case? is my cps even bad? soooo many questions!

 

It is checked while cranking at the plug going TO the CPS. Maybe you checked the harness side when it was unplugged.