Total loss here.... cranks, intermittent starting
01-18-2019, 04:01 PM
#1
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Thread Starter
Total loss here.... cranks, intermittent starting
Hi all, I’m at a loss on this one, it’s an intermittent problem that’s driving me up a wall. Here’s the short version of it. Parts that are new: starter, battery, CPS, ignition coil. When it’s cold I can start it right up no problem. I can take the key out and start it maybe one or two, even ten times over but once it warms up it’ll never start again. Also, it randomly cuts power for a second while driving down the road. Usually does this under load. I can’t for the life of my figure it out but i desperately need it for work. I don’t want to keep throwing parts at it cause money is tight right now. (In the coast guard.... not getting paid.) any help is greatly appreciated. Other things I’m thinking are, starter relay, starter solenoid, I’m grasping at straws at this point. Thanks in advance!
01-18-2019, 04:09 PM
#2
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Location: Groton, MA
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Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
What brand was the CPS? If it wasn't Mopar it's not to be trusted. What is the year/engine/transmission?
The first thing to do, and it won't cost you anything but your time, is to go through and check that all your ground points and battery cables connections are clean and tight. Don't just look at them, take them off, sandpaper the contact points clean and re-attach them so they are tight.
Also, you can test the relay with a multi-meter. There are several references online.
When it doesn't start - does it crank but won't fire up or does it not crank at all?
The first thing to do, and it won't cost you anything but your time, is to go through and check that all your ground points and battery cables connections are clean and tight. Don't just look at them, take them off, sandpaper the contact points clean and re-attach them so they are tight.
Also, you can test the relay with a multi-meter. There are several references online.
When it doesn't start - does it crank but won't fire up or does it not crank at all?
01-18-2019, 04:18 PM
#3
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Thread Starter
Thanks for the quick reply! I’ll have to do that tomorrow when I get some more sunlight. It wasn’t molar. Autozone special. 99 bucks. And it’ll crank all day long but won’t even sputter once it’s warmed up. It’s like the lights on but nobody’s home. A go/no go situation.
01-18-2019, 04:24 PM
#4
CF Veteran
thewhitestripes,
Please provide the vehicle year when you get a chance.
Go out, press the accelerator to the floor and try to start it. Does it try to stumble and run -even- when the accelerator is fully depressed?
Please provide the vehicle year when you get a chance.
Go out, press the accelerator to the floor and try to start it. Does it try to stumble and run -even- when the accelerator is fully depressed?
Last edited by jordan96xj; 01-18-2019 at 04:26 PM.
01-18-2019, 04:26 PM
#5
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Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
Jeez - A hundred bucks for the Autozone special!?! You could definitely get a Mopar for that price!
It's WIDELY recommended on this forum that if there is one part on the vehicle that MUST be Mopar, it's the CPS. You should try to find a Mopar part and return the Autozone one. The magnets on aftermarket replacements are vastly inferior and you're asking for trouble.
Assuming you have an automatic, you likely have a CPS that is getting too hot and failing. It's very very common - the Jeep drives great until it gets hot, then it stalls and won't start up until it cools down.
Do the grounds checking and relay testing just to be sure that stuff is good - but based on reading many, many posts of folks having the same symptoms you describe, I would strongly suggest the CPS is failing you.
Beyond that - you might also want to do a fuel pressure test. A failing fuel pump can have the same symptoms. Regardless of anything though, don't fire the parts cannon! In your case, you can cover the cost of a new Mopar CPS by returning the Autozone special, so I'd do that just to make sure you can get a Mopar one while there are still parts available... at some point the supply is going to run out.
It's WIDELY recommended on this forum that if there is one part on the vehicle that MUST be Mopar, it's the CPS. You should try to find a Mopar part and return the Autozone one. The magnets on aftermarket replacements are vastly inferior and you're asking for trouble.
Assuming you have an automatic, you likely have a CPS that is getting too hot and failing. It's very very common - the Jeep drives great until it gets hot, then it stalls and won't start up until it cools down.
Do the grounds checking and relay testing just to be sure that stuff is good - but based on reading many, many posts of folks having the same symptoms you describe, I would strongly suggest the CPS is failing you.
Beyond that - you might also want to do a fuel pressure test. A failing fuel pump can have the same symptoms. Regardless of anything though, don't fire the parts cannon! In your case, you can cover the cost of a new Mopar CPS by returning the Autozone special, so I'd do that just to make sure you can get a Mopar one while there are still parts available... at some point the supply is going to run out.
Last edited by PatHenry; 01-18-2019 at 04:30 PM.
01-18-2019, 06:16 PM
#6
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Year: 96
Model: Cherokee (XJ)
Engine: 4.0
other possibilities, in order of economy;
wiggle wire harness to ECU
relays in PDC can go intermittent (wiggle & squeeze them)
fuel pump, its wiring & earth...search other threads to assist fault-finding
wiggle wire harness to ECU
relays in PDC can go intermittent (wiggle & squeeze them)
fuel pump, its wiring & earth...search other threads to assist fault-finding
01-19-2019, 01:56 PM
#7
Junior Member
Thread Starter
it’s a 1997 XJ automatic. And no it doesn’t even try and stumble or run when the peddle is fully depressed.
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01-19-2019, 02:01 PM
#8
Junior Member
Thread Starter
thanks for the insight, I’ve wiggled all the wires and sometimesssss I feel like it works but once it’s warmed up nothing seems to work. I’ve swapped all the relays in all the combinations I can and it doesn’t make anything better or worse. I can hear the fuel pump prime every time I turn the key. It sounds pretty healthy. I’ll get a fuel pressure tester today though to verify.
01-19-2019, 02:07 PM
#9
Junior Member
Thread Starter
Jeez - A hundred bucks for the Autozone special!?! You could definitely get a Mopar for that price!
It's WIDELY recommended on this forum that if there is one part on the vehicle that MUST be Mopar, it's the CPS. You should try to find a Mopar part and return the Autozone one. The magnets on aftermarket replacements are vastly inferior and you're asking for trouble.
Assuming you have an automatic, you likely have a CPS that is getting too hot and failing. It's very very common - the Jeep drives great until it gets hot, then it stalls and won't start up until it cools down.
Do the grounds checking and relay testing just to be sure that stuff is good - but based on reading many, many posts of folks having the same symptoms you describe, I would strongly suggest the CPS is failing you.
Beyond that - you might also want to do a fuel pressure test. A failing fuel pump can have the same symptoms. Regardless of anything though, don't fire the parts cannon! In your case, you can cover the cost of a new Mopar CPS by returning the Autozone special, so I'd do that just to make sure you can get a Mopar one while there are still parts available... at some point the supply is going to run out.
It's WIDELY recommended on this forum that if there is one part on the vehicle that MUST be Mopar, it's the CPS. You should try to find a Mopar part and return the Autozone one. The magnets on aftermarket replacements are vastly inferior and you're asking for trouble.
Assuming you have an automatic, you likely have a CPS that is getting too hot and failing. It's very very common - the Jeep drives great until it gets hot, then it stalls and won't start up until it cools down.
Do the grounds checking and relay testing just to be sure that stuff is good - but based on reading many, many posts of folks having the same symptoms you describe, I would strongly suggest the CPS is failing you.
Beyond that - you might also want to do a fuel pressure test. A failing fuel pump can have the same symptoms. Regardless of anything though, don't fire the parts cannon! In your case, you can cover the cost of a new Mopar CPS by returning the Autozone special, so I'd do that just to make sure you can get a Mopar one while there are still parts available... at some point the supply is going to run out.
01-19-2019, 02:09 PM
#10
Junior Member
Thread Starter
Also, grasping at straws here, would oil on the flywheel cause the CPS to not get a good reading? I have a rear main seal leak, maybe the flywheel is spinning up some oil and cause the CPS to fail? Such a frustrating issue.... I garuntee if I go out there right now after not messing with it for an hour it’ll start right up.
01-19-2019, 02:16 PM
#11
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Year: 2001
Model: Cherokee (XJ)
Engine: 4.0L
Have you checked the ADS relay ? they do go bad in time , Let us know when you find the problem . I don't think oil would bother the crank sensor because the same type of sensor is used to read the crank though the block so it reads the crank in oil .
Last edited by tech; 01-19-2019 at 02:22 PM.
01-19-2019, 03:32 PM
#12
Junior Member
Thread Starter
Went out and bought the cap and rotor, made it there no problem, left it running, bought the parts and headed home no problem. Turned it off and tried to start it again. Nothing. Replaced the parts, started right up. Turned it off and tried to start it again. Nothing. This thing is driving me crazy.
01-19-2019, 04:16 PM
#13
Junior Member
Thread Starter
Little more info, once I can get the problem to arise (crank but no start) I tested the coil and spark isint even getting to it. So whatever the problem is it’s cutting spark to the whole system. Ignition coil is brand new
01-21-2019, 04:20 PM
#14
Junior Member
Thread Starter
Quick question, does the starting circuit also enable spark if working correctly? I know it turns the starter over but I thought spark was initiated by the ECU not the starter solinoid correct? Why wouldn’t I get power to my ignition coil if my starter was cranking over?
01-21-2019, 05:17 PM
#15
CF Veteran
Quick question, does the starting circuit also enable spark if working correctly? I know it turns the starter over but I thought spark was initiated by the ECU not the starter solinoid correct? Why wouldn’t I get power to my ignition coil if my starter was cranking over?
When the PCM is happy with the Cam/Crank relationship and RPM while the motor is cranking, it initiates ignition (spark) by providing ground to the ASD relay (control side) - this together with the ignition switch being in the Start or Run/On position will provide the positive required at the same ASD relay (control side) this will close the relay and allow 12v positive to the ignition coil. The PCM further controls ignition (spark) by pulsing a ground to the ignition coil which receives a constant 12v from the ASD relay (and ASD fuse), but the timing and pulsing of the ground at the ignition coil comes directly from the PCM.
So, some likely candidates for missing spark are a faulty ignition coil, failed Crankshaft Position Sensor, a failed Camshaft Position Sensor, faulty ignition switch, or failed ASD relay (and of course, this includes the wiring these things depend on). These aren't the only possibilities, but the more common ones.
Last edited by jordan96xj; 01-21-2019 at 05:23 PM.