Project Comanche Posted March 31, 2014 Share Posted March 31, 2014 I know this topic has been covered numerous times but I have reached wits end and do not know where to search next. The problem started as an intermittent start issue. Spark or no spark. No obvious reason to why it would or would not start. Cranked over fine. Suspected crankshaft sensor or ignition control module at first. New ICM later thought it was fixed. Few days later proved to NOT be fixed. Time for new crank sensor. New good quality sensor installed, proved to be not the problem a few days later. Cap and rotor seem fine. New symptoms today. Cranked motor over and was a no-start day. Tried a few more time only to find the evolving characteristic of zero cranking. Starter will no longer turn when ignition is cranked. Talked with a friend that is a mechanic at the local Chrysler/jeep dealer. He said it sounds like a bad PCM or ignition switch. He recommended the PCM due to disconnecting the battery while working on it(allowing the computer to reset) then the truck working for a few days then symptoms come back. Makes sense to me. This is a test I will try tomorrow. Second was the ignition switch. Can this cause a no spark and/or no crank symptom? Easy cheaper fix. I was also wondering if all these issues can be traced to grounding problems??? Coil? I didn't think a coil could produce intermittent issues, weak or no start sure but not like this In the end I will have a complete new ignition system and will have learned a ton along the way. Until then I need help. Any help, advice, experience, suggestions are greatly appreciated. Link to comment Share on other sites More sharing options...
BeenJaminJames Posted March 31, 2014 Share Posted March 31, 2014 Check and clean all your grounds thoroughly and clean the contacts in the big connector at the top driver side of the firewall above the brake booster. If that doesn't help, click over to this page and check everything listed. These renix 4.0's are notorious for electrical issues... http://comancheclub.com/topic/36382-cruisers-renix-tips/ Link to comment Share on other sites More sharing options...
88whitemanche Posted March 31, 2014 Share Posted March 31, 2014 When I had this issue...when I had someone crank for me I would shake either the c101 connector or the wires by the relay strip where the starter relay is located... Wherever it would start I would clean surfaces and retightened everything.... But you would need to freshen and add new grounds as per cruiser tips....in the link above Link to comment Share on other sites More sharing options...
Eagle Posted March 31, 2014 Share Posted March 31, 2014 Talked with a friend that is a mechanic at the local Chrysler/jeep dealer. He said it sounds like a bad PCM or ignition switch. He recommended the PCM due to disconnecting the battery while working on it(allowing the computer to reset) then the truck working for a few days then symptoms come back. Makes sense to me. This is a test I will try tomorrow. You don't have a PCM ... you have an ECU. It doesn't in any way interface with the starter motor, so it cannot cause a no crank failure. I don't think that's your problem. Link to comment Share on other sites More sharing options...
Project Comanche Posted March 31, 2014 Author Share Posted March 31, 2014 between checking grounds and connections are there any components that can cause a no spark/no crank symptom? Is the ignition switch even a viable guess? I will get to work tomorrow. Link to comment Share on other sites More sharing options...
Project Comanche Posted March 31, 2014 Author Share Posted March 31, 2014 Would bad grounds or connections also cause the motor to idle differently? Within the last week when the truck does decide to start, it has been idling as if it is going to die...hasn't yet, but does not idle consistantly. In a way the idle is surging. Link to comment Share on other sites More sharing options...
Eagle Posted March 31, 2014 Share Posted March 31, 2014 between checking grounds and connections are there any components that can cause a no spark/no crank symptom? Is the ignition switch even a viable guess? I will get to work tomorrow. IMHO the ONLY single component that can cause both no spark AND no crank is the ignition switch. However ... on an old vehicle, sometimes multiple problems hit at the same time. Have you tried jumping directly from the battery to the starter solenoid to verify that the starter and solenoid are good? Link to comment Share on other sites More sharing options...
BeenJaminJames Posted March 31, 2014 Share Posted March 31, 2014 between checking grounds and connections are there any components that can cause a no spark/no crank symptom? Would bad grounds or connections also cause the motor to idle differently? Within the last week when the truck does decide to start, it has been idling as if it is going to die...hasn't yet, but does not idle consistantly. In a way the idle is surging. What you have sounds just like classic bad ground issues. These renix 4.0's are notorious for wiring problems. You've got a few grounds that are common failure points and can cause erratic issues including intermittent no-starts, poor idle, and all sorts of general driveability issues, especially the one on the passenger side of the block at the dipstick mounting stud. The big C101 connector above the brake booster is also a very common failure point and can cause all sorts of driveability issues and intermittent no-starts. Another common failure point is the CPS on the bellhousing. Sometimes they'll go bad completely, sometimes they'll test good when measuring impedance but won't produce a strong enough signal to run the ECU. Unplug it, probe the connector on the sensor side, set your meter to ACVolts, and crank the truck over. You want at least a .5V signal. There are detailed instructions and pictures on how to locate and clean the grounds, C101, and test/adjust the CPS in the thread I linked above. I dealt with every kind of mysterious issue imaginable on my truck, and had to figure it all out myself, before I found that page of Cruiser's tips. Every single electronic issue I've had with my truck so far, is covered on that page, they are very common failure points that rear their heads on every single renix 4.0 soner or later. If I'd just gone down that list and taken care of everything when I first got the truck I would've never had any of the issues in the first place. I highly reccommend you start there. As far as your no-crank issue, it's likely a seperate issue not related. Test the solenoid mounted on the side of the starter, and test the solenoid under the hood by the battery. Link to comment Share on other sites More sharing options...
Project Comanche Posted March 31, 2014 Author Share Posted March 31, 2014 Cleaned the grounds today. Everything seems to be mended. Only time will tell. Definately a learning experience for troubleshooting and spending zero money before replacing parts. Thank you everyone for your help. I feel like I am almost a jeep ignition expert. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 3, 2014 Share Posted April 3, 2014 Cleaned the grounds today. Everything seems to be mended. Only time will tell. Definately a learning experience for troubleshooting and spending zero money before replacing parts. Thank you everyone for your help. I feel like I am almost a jeep ignition expert. If it were me, I would also do tips 2 through 5 in my signature link. Good lesson learned so far, eh? LOL. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 8, 2014 Author Share Posted April 8, 2014 After checking grounds my MJ started to work, today it decided to quit again. I do not understand what causes my frustrating scenarios. I do not understand the cause. I guess I will continue on down the list of connections to check along the above posted list. Any other suggestions would be greatly appreciated. Link to comment Share on other sites More sharing options...
gogmorgo Posted April 8, 2014 Share Posted April 8, 2014 Does it crank? You mentioned a no-crank issue above. A dirty neutral safety switch (NSS) lead to an intermittent no-crank on my '91. Starting in neutral usually worked, if not I wound up shorting the solenoid which always did the trick. This won't affect a vehicle's running, though, just whether or not it cranks over. Mostly, though, I'm posting because your sig says you have an "AX-4, 4 spd auto". Which is it? The four-speed automatic transmission is the AW4, and the AX-4 is a four-speed manual. The neutral safety switch is different between the autos and manuals. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 12, 2014 Author Share Posted April 12, 2014 Sorry about that... My mistake. It is a AW4. I am continuing to have issues. As I stated before I cleaned the grounds and believed that to be the culprit... It has continued to intermittently start. When it decides not to start I can turn the motor over and get fuel but no spark AND/OR the key turns the fuel pump on and the jeep but will not crank at all. When key is turned to the start position it is as if the ignition switch turns everything off. The ignition switch can be the culprit of the second symptom... Can it also cause a no start symptom? I have changed crank sensor, ICM, checked grounds/cleaned, checked all connections and cleaned the C101, and need the truck to be reliable for trails this summer, not to mention get me to work AND start when I need to come home. Link to comment Share on other sites More sharing options...
Eagle Posted April 13, 2014 Share Posted April 13, 2014 I am continuing to have issues. As I stated before I cleaned the grounds and believed that to be the culprit... It has continued to intermittently start. When it decides not to start I can turn the motor over and get fuel but no spark AND/OR the key turns the fuel pump on and the jeep but will not crank at all. When key is turned to the start position it is as if the ignition switch turns everything off. The ignition switch can be the culprit of the second symptom... Can it also cause a no start symptom? The reason turning the key to the START position seems to turn everything off is that turning the key to the START position turns everything off. As the saying goes, "That's a feature, not a bug." The system is designed to operate that way. The one thing that should continue to function when cranking (besides the starter motor itself, of course) is the fuel pump. But that brings us to another little part that can create problems: the fuel pump ballast resistor. I don't know if it can go into an intermittent failure mode but ... why not? During normal engine operation, the ballast resistor drops the voltage to the fuel pump to about 9 volts to reduce noise. During engine cranking, there's a bypass circuit that sends a full 12 volts to the fuel pump. In the case a really bad ballast resistor, the engine will start when the fuel pump runs during cranking, then after the key is released to the RUN position the fuel pump cuts out and a few seconds later the engine dies. The 87 4.0L didn't have a ballast resistor. It's safe to run without it, so you could try jumpering yours and see if it makes a difference. Link to comment Share on other sites More sharing options...
Megadan Posted April 13, 2014 Share Posted April 13, 2014 Honestly, I would replace the ignition switch as it sounds like a very likely culprit. That, and they really aren't very expensive anyway, unless you are on a tight budget.Have you also checked or replaced the starter relay? If the ignition switch isn't the culprit, a relay can sometimes go bad and have intermittent work/not work issues. I ran into that before on a car with my headlights. It's worth looking into, and also not a very expensive thing to replace if necessary. It could simply be a matter of a loose connection on the starter relay, or a wire that may be shorting out on something.Have you tested or replaced the ignition coil by chance? I doubt it's the problem, but it never hurts to be thorough. I know on my 1988 it wasn't a leading problem, but it did contribute to making other problems worse. They don't always just fail, but sometimes die a slow death, and eventually get very weak like mine did. Just tossing that out there as something to think on.Try and keep a cool head and be methodical. Once you have ruled out the common headache causes via Cruisers guide and still have a proble you can then take logical steps to diagnose, and start with the most likely cause. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 13, 2014 Author Share Posted April 13, 2014 I'll check on those things today. Just got home from work and tried to start it just out of curiosity... Didn't start. It almost made me happy that it is beginning to be consistent. If this is true when I find the problem it will start and be fixed! Link to comment Share on other sites More sharing options...
Minuit Posted April 13, 2014 Share Posted April 13, 2014 The NSS can cause a no crank condition. It's free to clean so you may want to look there also. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 14, 2014 Author Share Posted April 14, 2014 Now it consistently cranks and won't start. Tomorrow I am going to recheck the grounds and all connections. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 14, 2014 Author Share Posted April 14, 2014 Now it consistently cranks and won't start. Tomorrow I am going to recheck the grounds and all connections. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 14, 2014 Author Share Posted April 14, 2014 Rechecked on ground next to dipstick. Looked fine from when I cleaned it a few weeks ago. Tried starting it after and it started. No idea if that was the cause or not. There is a small single wire plug near the dipstick ground... Does anyone know what this is for or where it should be connected? Mine is just hanging out. Link to comment Share on other sites More sharing options...
Megadan Posted April 14, 2014 Share Posted April 14, 2014 Is it a plug, or just a hoop electrical terminal? I don't know if the 87's are any different, but my 88 has two wires that go to the dipstick tube along with the big ground cable. Those two other wires are the ignition and ecu grounds. At least as far as I know they are. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 15, 2014 Author Share Posted April 15, 2014 Started yesterday no problems. Will not start today. First off can anyone identify these two open connections? I truly am stumped on this intermittent start issue. Is ignition switch even a likely culprit? I do not know where else to look. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 15, 2014 Author Share Posted April 15, 2014 Started yesterday no problems. Will not start today. First off can anyone identify these two open connections? I truly am stumped on this intermittent start issue. Is ignition switch even a likely culprit? I do not know where else to look. Link to comment Share on other sites More sharing options...
Project Comanche Posted April 15, 2014 Author Share Posted April 15, 2014 Also relay with no relay on drivers side... Does anyone know what it could be for? Link to comment Share on other sites More sharing options...
sloride Posted April 15, 2014 Share Posted April 15, 2014 Have you messed with the cap and rotor at all? I had a faulty rotor on a chevy nova years ago that gave me similar issues to what you're experiencing. Link to comment Share on other sites More sharing options...
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