Luvtohunt Posted April 20, 2012 Share Posted April 20, 2012 My MJ has had a hard time starting lately, where it will start or just keep turning over and never fire. I was also driving it today and it suddenly died, but the radio was still on. So i was wondering is it the fuel pump or is it something else going out on it? Thank you Link to comment Share on other sites More sharing options...
Eagle Posted April 20, 2012 Share Posted April 20, 2012 It could be the CPS (Crankshaft Position Sensor) It could be the fuel filter It could be the coil/ignition module How old is your CPS? Link to comment Share on other sites More sharing options...
ncmountainMJ Posted April 21, 2012 Share Posted April 21, 2012 redo your grounds..... especially the block ground by the oil fill... I did it and MAN what a difference.... Link to comment Share on other sites More sharing options...
mknherhappy Posted April 22, 2012 Share Posted April 22, 2012 It could be the CPS (Crankshaft Position Sensor) It could be the fuel filter It could be the coil/ignition module How old is your CPS? Does the CPS need to be changed often? How are is it to change? Link to comment Share on other sites More sharing options...
Luvtohunt Posted April 22, 2012 Author Share Posted April 22, 2012 It could be the CPS (Crankshaft Position Sensor) It could be the fuel filter It could be the coil/ignition module How old is your CPS? The fuel pump is probably not suspect then? Thank you for the replies Link to comment Share on other sites More sharing options...
cruiser54 Posted April 23, 2012 Share Posted April 23, 2012 It could be the CPS (Crankshaft Position Sensor) It could be the fuel filter It could be the coil/ignition module How old is your CPS? The fuel pump is probably not suspect then? Thank you for the replies Hate to seem like a butthead, but we need more info: From Joe Peters and well stated. Sounds harsh but just makes sense: “Let’s play a game. You pretend that you are the only one that knows what year/engine, etc that you are asking about. We will all pretend you never asked a question until you provide at least the bare minimum of information about your vehicle”. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 23, 2012 Share Posted April 23, 2012 It could be the CPS (Crankshaft Position Sensor) It could be the fuel filter It could be the coil/ignition module How old is your CPS? The fuel pump is probably not suspect then? Thank you for the replies Hate to seem like a butthead, but we need more info: From Joe Peters and well stated. Sounds harsh but just makes sense: “Let’s play a game. You pretend that you are the only one that knows what year/engine, etc that you are asking about. We will all pretend you never asked a question until you provide at least the bare minimum of information about your vehicle”. Link to comment Share on other sites More sharing options...
Luvtohunt Posted April 23, 2012 Author Share Posted April 23, 2012 Its a 1988 Comanche 4.0L 6 cyl, 4x4 just over 103,000 miles, I know I've changed the oxygen sensor but no others have been changed to my knowledge. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 23, 2012 Share Posted April 23, 2012 You need to do some testing. Some symptoms can be caused by different component failures. If I were you, I would start with testing the CPS per the following instructions. 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 Then, I would perform this procedure just to eliminate it as a possibility: 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 Link to comment Share on other sites More sharing options...
MJCARENA Posted April 23, 2012 Share Posted April 23, 2012 Thanks cruiser54 for this info on the ICU/Coil and CPS. I am not having problems, but will check this out anyway. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 23, 2012 Share Posted April 23, 2012 MJCARENA, there's a compilation of almost all my write-ups pertaining to Renix Jeeps at www.jeepseekers.com under the Help and Resources tab. Any questions or comments, post 'em up. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now