aerocorey Posted March 15, 2008 Share Posted March 15, 2008 I'm still having the no-start. Fuel pump is priming as it should. I've replaced the CPS and wired it directly to the engine harness with butt connectors. I've replaced the module, coil, wires, cap, rotor, plugs, battery cables, cam position sensor (stator, pick-up, whatever you want to call it), and cleaned every connection I can get to. It'll go days without a problem, then all of the sudden it won't start. Spark tester says I have no spark from the coil. It never dies once started. It cranks every time, just no fire. I have roll started it down a hill several times when it wouldn't start by itself. I've replaced the 3 relays next to the starter relay. I've cleaned the contacts on the starter relay. I've had the battery tested, it's good. Alternator is charging. Anytime it doesn't start I can walk away from it for 15-20 minutes and it'll start fine. Occasionally if I sit there and crank it for eternity it'll light off, but I don't like doing that. Only parts left are the battery, computer, starter relay, and starter. Battery doesn't make sense because it's been tested good. It's got plenty of water in it too, no leaks. When it won't start it'll crank, and crank, and crank...battery has taken the punishment of cranking for weeks and hasn't failed me yet. Computer is possible I suppose, but I'm told they don't die. Starter relay doesn't make sense because it cranks like it should. Starter could be drawing too many amps, but it isn't killing the battery. I threw a booster battery on it and tried it a few minutes ago at NAPA when it wouldn't start. It cranked for 10 sec without starting. I let go of the key, counted to 10, and tried again. It started after 7 seconds, but it had been about 20 minutes since I shut it off last so it could have been a coincidence. 10 minutes after that I shut it off at the grocery store. When I came out after shopping it started exactly as described at NAPA, but without the booster battery. I need suggestions. Link to comment Share on other sites More sharing options...
james750 Posted March 15, 2008 Share Posted March 15, 2008 I donat think it is ur starter if it is cranking. if it is a stick u can test and see if the gear in there is moving in and out of place as it should by cranking it on a flat slope and seeing if the car rolls forward. However, DO NOT let it roll off of the starter crank for more than a few seconds because it is really bad on ur starter. will it pop start (only if it is a manual)? Link to comment Share on other sites More sharing options...
aerocorey Posted March 15, 2008 Author Share Posted March 15, 2008 The engine is turning over everytime I turn the key, and the truck starts fine once I let it sit. Why whould I need to crank it in gear and beat on the starter like that? The problem it's been suggested my starter could have is drawing too many amps while starting. This could leave too few amps for the coil to make spark with. This is an entertaining theory, but the starter isn't killing the battery so I don't think it's the problem. Yes, it pop starts. Link to comment Share on other sites More sharing options...
james750 Posted March 15, 2008 Share Posted March 15, 2008 Ok, i didnt realize the truck was starting at all (I should really start reading more into posts b4 posting :roll: ). it is not neccisary to do that then. the starter is fine. i have no clue where to go from here since it is pop starting fine and the starter is turning over. Idk really know what the problem is from here. My dads xj had a problem where the fuel pump was priming but wouldnt stay up to pressure so it took an eternity of cranking to start it. But this still doesnt sound right. :???: Link to comment Share on other sites More sharing options...
aerocorey Posted March 15, 2008 Author Share Posted March 15, 2008 Fuel pump is priming. Fuel pressure is good. Spark tester says it's not starting because it's not making spark. This thing is SCREAMING crank sensor, but I've replaced it. Could it be dirty notches in the flywheel? I've found references about ohming the CPS out with the truck off to test it, but is there a way to test it with the truck running? If I throw a multimeter on it during cranking with it connected should I see voltage? Does the Renix system continue reading the CPS once the truck is running? The guy at NAPA said all it does is look for 2 flashes fron the CPS during cranking and compares it to the cam position sensor. He says once it has the relationship between the CPS and cam sensor locked in it ignores the CPS and uses the can sensor for everything. I'm reluctant to rely on heresay fron the NAPA guy. Link to comment Share on other sites More sharing options...
Oizarod115 Posted March 15, 2008 Share Posted March 15, 2008 could be a bad CPS from the store or you could try another ECU i'm sure someone here has one Link to comment Share on other sites More sharing options...
aerocorey Posted March 15, 2008 Author Share Posted March 15, 2008 could be a bad CPS from the store or you could try another ECU i'm sure someone here has one New CPS tests good. Old CPS tested good too. ECU is my next guess, but that's all it is...a guess. Anyone near Austerlitz, NY with an ECU I can get today? I'm at the in-laws right now. I'm running out of time with this truck. It's in the classified section right now... Link to comment Share on other sites More sharing options...
NewToJeeps Posted March 15, 2008 Share Posted March 15, 2008 I am very very new to working on jeeps. However i have a headache made by Geo that had the same problem. I had to replace the little sensor/safety switch that is on the clutch pedal. It had taken a bit of abuse and was working only part of the time. it sounds as if you are describing the same thing mine was doing. I could be very wrong but its an idea of something cheep to check into. Link to comment Share on other sites More sharing options...
aerocorey Posted March 15, 2008 Author Share Posted March 15, 2008 I am very very new to working on jeeps. However i have a headache made by Geo that had the same problem. I had to replace the little sensor/safety switch that is on the clutch pedal. It had taken a bit of abuse and was working only part of the time. it sounds as if you are describing the same thing mine was doing. I could be very wrong but its an idea of something cheep to check into. There is no NSS or clutch safety switch on a 5 speed MJ. If there was a switch on a 5 speed MJ it wouldn't be the problem because the engine cranks when I turn the key. If it was a bad NSS or clutch safety switch it wouldn't even do that. Does anyone know enough about the ECU to give me an idea if that could be the problem? It roll starts fine when it won't start itself, and it cranks everytime...that's what really gets me confused. Link to comment Share on other sites More sharing options...
james750 Posted March 15, 2008 Share Posted March 15, 2008 Not only does it not have an NSS (only in the autos on Jeeps) but even if it did it wouldnt be the problem because NSS stops the starter from cranking. Link to comment Share on other sites More sharing options...
NewToJeeps Posted March 15, 2008 Share Posted March 15, 2008 As i said I'm new to the jeep world. Geo and Jeep are to different animals but it was just an idea. Thanks for the corrected info ! Link to comment Share on other sites More sharing options...
Eagle Posted March 15, 2008 Share Posted March 15, 2008 None of this makes sense, so start thinking outside of the box. When it doesn't start, you have no spark. That could indicate a bad CPS, or a bad coil/ignition module. But ... neither of those two items are in any way affected or bypassed if you roll the truck down a hill and pop the clutch, yet if you roll it -- it starts. We're overlooking something very basic here. I don't claim to know what it is, but I'll be worrying about it this evening. Meanwhile, guys, stop tossing out the cookie cutter answers and think about what could cause no spark when cranking but allow spark for a drop start. Link to comment Share on other sites More sharing options...
aerocorey Posted March 15, 2008 Author Share Posted March 15, 2008 start thinking outside of the box...stop tossing out the cookie cutter answers and think... x2 I'm really up against it here. I don't want to discourage anyone from making suggestions because I obviously can't figure it out for myself, but I'm a pretty handy guy. I'm admittadly behind the learning curve with this particular model truck, but I make my living using diagrams and fault trees to diagnose/repair fighter jets. If it was something simple I would have nailed it by now. I have 1 full day left in the area before I leave the truck at my in-laws and move away. They're good folks. I don't want to leave them a tempermental truck to babysit. Dirty flywheel notches? Dirty sensor? Sticking relay inside the ECU? Bad ground? Ignition switch? Link to comment Share on other sites More sharing options...
Eagle Posted March 15, 2008 Share Posted March 15, 2008 I wish I had time to get you the wiring diagrams. I'm leaning toward ignition switch, but I haven't had time to look through the wiring book -- not that I could understand it if I did. (I HATE the Jeep wiring diagrams. I'm accustomed to the old AMC diagrams, where you could follow a wire from one end to the other without having to look at 17 different pages.) Is there anything in the ignition switch that bypasses a circuit when it's in the START position? We know the ballast resistor for the fuel pump gets bypassed during starts. That's not the issue here, since the fuel pump runs and pressurizes the system. But is there any other circuit, leading to the coil, that gets bypassed, that might have a fault in the bypass circuit? Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 15, 2008 Share Posted March 15, 2008 Well, if it was an HO I'd say the ASR (auto shutdown relay) is fubar. I had one sticking on my rig and it caused similar erratic starting symptoms. If it sticks it shuts down power to the coil. But I'm not sure if the Renix models had them...... :eek: Link to comment Share on other sites More sharing options...
aerocorey Posted March 16, 2008 Author Share Posted March 16, 2008 I wish I had time to get you the wiring diagrams. I'm leaning toward ignition switch, but I haven't had time to look through the wiring book -- not that I could understand it if I did. (I HATE the Jeep wiring diagrams. I'm accustomed to the old AMC diagrams, where you could follow a wire from one end to the other without having to look at 17 different pages.) Is there anything in the ignition switch that bypasses a circuit when it's in the START position? We know the ballast resistor for the fuel pump gets bypassed during starts. That's not the issue here, since the fuel pump runs and pressurizes the system. But is there any other circuit, leading to the coil, that gets bypassed, that might have a fault in the bypass circuit? According to Haynes, the module and ECU get 12V from the ignition switch in ON and START from the same wire. There's a plug in diagnostic connector 2 that I can test for 12V there. I'll check it next time. In START the ECU gets another 12V signal from the starter relay. I assume this signal is so the ECU will advance ignition timing for starting. I wonder if it's a bad ECU ground. Anyone know where I should look for that? The succesful roll starts make that unlikely too... Well, if it was an HO I'd say the ASR (auto shutdown relay) is fubar. I had one sticking on my rig and it caused similar erratic starting symptoms. If it sticks it shuts down power to the coil. But I'm not sure if the Renix models had them...... :eek: There's something called the "B+ latch relay". I don't know what that does. Anyone know? There's also an O2 sensor relay, and we all know about the fuel pump relay. I bought a new relay and switched it out for each of those 3 relays when it didn't start at NAPA earlier today. No difference. Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 16, 2008 Share Posted March 16, 2008 Here's some good reading; similar problem like yours. Turned out to be the ECU: http://www.naxja.org/forum/showthread.php?t=71001&highlight=shutdown+relay Link to comment Share on other sites More sharing options...
dragonrider477 Posted March 16, 2008 Share Posted March 16, 2008 there is a green wire going from the starter solenoid to the computer.it's purpose is to tell the computer the starter is cranking the engine and obviously the computer should take the suggestion to get it's ducks in a row and start the fuel and spark events so it will run. this cranking signal comes off the terminal that goes to the starter.there are 2 connectors on the computer.a24 pin and a 32 pin.the green wire you are looking for is on the 32 pin plug and is labelled c3.you might try as a test to disconnect this wire from the computer and then see if it starts.if it still starts with this wire removed from the computer then this is not a source of the problem and you need to look elsewhere.if it fails to start we then know for sure that the computer needs this signal to start the truck.if that is the case, hook the wire back up to the computer and wire a test light or a buzzer or anything else that will measure the 12v signal on this wire while cranking.next time it does'nt start,monitor this signal.no light means that you have a harness problem somewhere between the solenoid and the computer.if the green wire has good power (cranking voltage shoud be at least 9.5 v to be a reliable signal)while cranking and the jeep is a no start most likely you will need to try a different computer as it is likely going bad intermittently Link to comment Share on other sites More sharing options...
aerocorey Posted March 16, 2008 Author Share Posted March 16, 2008 there is a green wire going from the starter solenoid to the computer.it's purpose is to tell the computer the starter is cranking the engine and obviously the computer should take the suggestion to get it's ducks in a row and start the fuel and spark events so it will run. this cranking signal comes off the terminal that goes to the starter.there are 2 connectors on the computer.a24 pin and a 32 pin.the green wire you are looking for is on the 32 pin plug and is labelled c3.you might try as a test to disconnect this wire from the computer and then see if it starts.if it still starts with this wire removed from the computer then this is not a source of the problem and you need to look elsewhere.if it fails to start we then know for sure that the computer needs this signal to start the truck.if that is the case, hook the wire back up to the computer and wire a test light or a buzzer or anything else that will measure the 12v signal on this wire while cranking.next time it does'nt start,monitor this signal.no light means that you have a harness problem somewhere between the solenoid and the computer.if the green wire has good power (cranking voltage shoud be at least 9.5 v to be a reliable signal)while cranking and the jeep is a no start most likely you will need to try a different computer as it is likely going bad intermittently That's good thinking. Anyone know more about what the ECU does before I start cutting wires to the ECU to see what they do? Link to comment Share on other sites More sharing options...
dragonrider477 Posted March 16, 2008 Share Posted March 16, 2008 I wish I had time to get you the wiring diagrams. I'm leaning toward ignition switch, but I haven't had time to look through the wiring book -- not that I could understand it if I did. (I HATE the Jeep wiring diagrams. I'm accustomed to the old AMC diagrams, where you could follow a wire from one end to the other without having to look at 17 different pages.) Is there anything in the ignition switch that bypasses a circuit when it's in the START position? We know the ballast resistor for the fuel pump gets bypassed during starts. That's not the issue here, since the fuel pump runs and pressurizes the system. But is there any other circuit, leading to the coil, that gets bypassed, that might have a fault in the bypass circuit? According to Haynes, the module and ECU get 12V from the ignition switch in ON and START from the same wire. There's a plug in diagnostic connector 2 that I can test for 12V there. I'll check it next time. In START the ECU gets another 12V signal from the starter relay. I assume this signal is so the ECU will advance ignition timing for starting. I wonder if it's a bad ECU ground. Anyone know where I should look for that? The succesful roll starts make that unlikely too... Well, if it was an HO I'd say the ASR (auto shutdown relay) is fubar. I had one sticking on my rig and it caused similar erratic starting symptoms. If it sticks it shuts down power to the coil. But I'm not sure if the Renix models had them...... :eek: There's something called the "B+ latch relay". I don't know what that does. Anyone know? There's also an O2 sensor relay, and we all know about the fuel pump relay. I bought a new relay and switched it out for each of those 3 relays when it didn't start at NAPA earlier today. No difference. the b latch relay leaves the computer powered up for a short time to allow it to pre-position the idle motor for the next start.the o2 relay i believe is for powering the heated part of the 02 sensor.the 91 up HO chrysler system did have asd relay issues.the engineers used that relay to power up way too many things,(injectors,coil +,fuel pump,02 sensor heater,and others).i have seen a shorted 02 heater cause a no start on one of these systems.not the best design imho. Link to comment Share on other sites More sharing options...
maddzz1 Posted March 16, 2008 Share Posted March 16, 2008 I had a similar problem but not exactly the same. The solution to mine was a bad wire behind the battery next to the fusible link. I'm not sure exactly which wire because I finally brought it too a auto electronics shop. Link to comment Share on other sites More sharing options...
aerocorey Posted March 16, 2008 Author Share Posted March 16, 2008 Read the entire CPS recall a minute ago. I'm gonna rewire my CPS more to the letter of that recall before I try anything else. Link to comment Share on other sites More sharing options...
dragonrider477 Posted March 16, 2008 Share Posted March 16, 2008 Read the entire CPS recall a minute ago. I'm gonna rewire my CPS more to the letter of that recall before I try anything else.good idea.the fact that your truck never dies once it is running might suggest that some unwanted resistance in the cps wiring may be weakening the signal just enough to cause a no start while cranking.when you "ROLL" start it by popping the clutch your system voltage is higher due to no starter activation which might be just enough to "boost" the signal to a level that the computer can interpit.that signal,under the best of conditions is'nt very strong so anything that deteriorates it will cuase a hard/no start condition. good luck! Link to comment Share on other sites More sharing options...
chicofuentes0224 Posted March 16, 2008 Share Posted March 16, 2008 Core, is there anyway you can buy a cheap starter or borrow someone elses. I had a similar problem on a Jetta VW back in 93. Everytime I drove a long distance it wouldn't start right away. I had to wait hours though to get it to restart. I replaced the starter and the problem went away. It had something to do with a defective starter. Just throwing my experience out there. Don't know if it will help. Link to comment Share on other sites More sharing options...
aerocorey Posted March 16, 2008 Author Share Posted March 16, 2008 Core, is there anyway you can buy a cheap starter or borrow someone elses. I had a similar problem on a Jetta VW back in 93. Everytime I drove a long distance it wouldn't start right away. I had to wait hours though to get it to restart. I replaced the starter and the problem went away. It had something to do with a defective starter. Just throwing my experience out there. Don't know if it will help. That's on the list, but I wouldn't get a cheap one. I'm gonna rewire my CPS first. If that doesn't fix it I'll keep trying stuff. Link to comment Share on other sites More sharing options...
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