Shane Posted July 12, 2012 Share Posted July 12, 2012 Went out to go to work yesterday and my mj wouldn't start. The motor turns over, but it won't start. It's an 89 4x4 auto. 4.0. I replaced the ignition module and the ignition coil and still not change. Any ideas as to what it might be? I have been told that it mybe the distributor or the crankshaft psotion sensor. Any othe possibilities or arethose even posibilities. As I have sadi many times on here I am not a mechanic and don't claim to be one, but I enjoy reading and researching on these trucks and fixing them. Any advice is appreciated. Link to comment Share on other sites More sharing options...
landlubber Posted July 12, 2012 Share Posted July 12, 2012 is it getting spark and fuel? Link to comment Share on other sites More sharing options...
Pete M Posted July 12, 2012 Share Posted July 12, 2012 get yourself a spark checker. little thing that plugs in between the plug and plug wire and lights up when the spark goes through. :thumbsup: Link to comment Share on other sites More sharing options...
ftpiercecracker1 Posted July 12, 2012 Share Posted July 12, 2012 The coil and module where a good place to start, but before you spend any more money check for the essentials FIRE, FUEL, and AIR 1. pull a couple of plugs and make sure spark is getting to the cylinders 2. test fuel pressure, if yours is injected, there is a nipple on the end of the fuel rail that can be tested with a pressure tester, if yours is carbed, i guess you could just pull the incoming fuel line and. . . a. if its a mechanical pump, just turn the engine over a couple times and have someone report if fuel is coming through the line b. if the pump is electric just turn the key on, might take a few trys, and have someone watch the line 3. air, just make sure nothing is clobberd up, other than that i don't know what to tell ya. there are a LOT of other things that can keep your truck from starting, but these are some of the first steps i like to take when dealing with a new problem. Hope it helps :wavey: Link to comment Share on other sites More sharing options...
Shane Posted July 12, 2012 Author Share Posted July 12, 2012 is it getting spark and fuel? Yes, It's getting spark and fuel. :clapping: I forgot to mention that. :doh: Link to comment Share on other sites More sharing options...
cruiser54 Posted July 12, 2012 Share Posted July 12, 2012 is it getting spark and fuel? Yes, It's getting spark and fuel. :clapping: I forgot to mention that. :doh: Well then, it's either getting not enough fuel or not good enough spark. How did you test for this? Link to comment Share on other sites More sharing options...
landlubber Posted July 12, 2012 Share Posted July 12, 2012 it should have a schrader valve at the rail for testing fuel pressure with a fuel pressure gauge, iirc it should be somewhere in the 40 lbs ballpark. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 12, 2012 Share Posted July 12, 2012 it should have a schrader valve at the rail for testing fuel pressure with a fuel pressure gauge, iirc it should be somewhere in the 40 lbs ballpark. I know that, but does the OP know that? 31 PSI with the vacuum hose on the fuel pressure regulator, 39 PSI with the vacuum disconnected. Link to comment Share on other sites More sharing options...
Shane Posted July 13, 2012 Author Share Posted July 13, 2012 is it getting spark and fuel? Yes, It's getting spark and fuel. :clapping: I forgot to mention that. :doh: Well then, it's either getting not enough fuel or not good enough spark. How did you test for this? Like I said, "I'm no mechanic and do not claim to be one." My father-in-law tested those things while I was at work one day. He said that he thought it was the distributor or the crank shaft position sensor. I just prefer to get a diagnose from true comanche people to make sure that I am fixing the right thing and not spending money on something that doesn't need it right now. Link to comment Share on other sites More sharing options...
cruiser54 Posted July 13, 2012 Share Posted July 13, 2012 is it getting spark and fuel? Yes, It's getting spark and fuel. :clapping: I forgot to mention that. :doh: Well then, it's either getting not enough fuel or not good enough spark. How did you test for this? Like I said, "I'm no mechanic and do not claim to be one." My father-in-law tested those things while I was at work one day. He said that he thought it was the distributor or the crank shaft position sensor. I just prefer to get a diagnose from true comanche people to make sure that I am fixing the right thing and not spending money on something that doesn't need it right now. Then check the fuel pressure with a gauge. And check the CPS output like this: 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 Link to comment Share on other sites More sharing options...
Shane Posted July 13, 2012 Author Share Posted July 13, 2012 is it getting spark and fuel? Yes, It's getting spark and fuel. :clapping: I forgot to mention that. :doh: Well then, it's either getting not enough fuel or not good enough spark. How did you test for this? Like I said, "I'm no mechanic and do not claim to be one." My father-in-law tested those things while I was at work one day. He said that he thought it was the distributor or the crank shaft position sensor. I just prefer to get a diagnose from true comanche people to make sure that I am fixing the right thing and not spending money on something that doesn't need it right now. Then check the fuel pressure with a gauge. And check the CPS output like this: 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 Tested CPS using a volt meter. According to Haynes Repair Manual, it should show no continuity. It tested at roughly 241. Am I correct in assuming that is the problem? If so what causes these things to go out? Age? :thumbsup: Thanks again brother for all the help!!!!! Link to comment Share on other sites More sharing options...
cruiser54 Posted July 14, 2012 Share Posted July 14, 2012 is it getting spark and fuel? Yes, It's getting spark and fuel. :clapping: I forgot to mention that. :doh: Well then, it's either getting not enough fuel or not good enough spark. How did you test for this? Like I said, "I'm no mechanic and do not claim to be one." My father-in-law tested those things while I was at work one day. He said that he thought it was the distributor or the crank shaft position sensor. I just prefer to get a diagnose from true comanche people to make sure that I am fixing the right thing and not spending money on something that doesn't need it right now. Then check the fuel pressure with a gauge. And check the CPS output like this: 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 Tested CPS using a volt meter. According to Haynes Repair Manual, it should show no continuity. It tested at roughly 241. Am I correct in assuming that is the problem? If so what causes these things to go out? Age? :thumbsup: Thanks again brother for all the help!!!!! Test it using the above instructions. Haynes sucks. Link to comment Share on other sites More sharing options...
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