1996 cherokee no power to coil
03-05-2018, 10:48 AM
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Model: Cherokee(SJ)
1996 cherokee no power to coil
I have no spark or power to coil. I’ve replaced the cps with no avail. I hear the ads and fuel pump relays cycle when I turn the key, but they cycle off within a second. I have power to the cps and the 5v outlets on the pcm seem to operate properly. What other sensors could cause this and how do I test this. Is it possible I installed the cps incorrectly.
03-05-2018, 11:54 AM
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If you hear the ASD relay cycling, then the next step is to test it to ensure it is functioning correctly. If it is, that will help rule out the ignition switch. When the ignition switch is ruled out, the 2 sensors that are most implicated would be the crankshaft position sensor and the camshaft position pickup (it is under the distributor cap).
CPS could be bad out of the box. Doesn't even have to be failed (as in wire/circuits could be fine). Could just be producing a signal that the computer isn't happy interpreting. The only way to confirm/rule-out is with a scope or by swapping a known-good in its place.
Many cheap CPS sensors are known for failed-in-box and producing signals that are close to OEM spec, but just off enough to cause start and running problems (multi-cylinder misfires at higher rpms seem to be a common symptom of non-oem CPS). The computer is pretty particular about the CPS signal, and this is why many recommend that it only be replaced with a Mopar sensor.
Camshaft pickup sensors are generally pretty cheap and an easy job (10 minutes or so).
CPS could be bad out of the box. Doesn't even have to be failed (as in wire/circuits could be fine). Could just be producing a signal that the computer isn't happy interpreting. The only way to confirm/rule-out is with a scope or by swapping a known-good in its place.
Many cheap CPS sensors are known for failed-in-box and producing signals that are close to OEM spec, but just off enough to cause start and running problems (multi-cylinder misfires at higher rpms seem to be a common symptom of non-oem CPS). The computer is pretty particular about the CPS signal, and this is why many recommend that it only be replaced with a Mopar sensor.
Camshaft pickup sensors are generally pretty cheap and an easy job (10 minutes or so).
03-06-2018, 11:45 AM
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Excellent reply Jordan and that’s just the answer I was looking for. I don’t think it’s my ignition. The ignition is turning on the pcm, though I’m just not getting power to the coil. The ASD relay is operating successfully, but as said, cycles off about 1 second after ignition is turned on. The cam shaft sensor is a very good possibility. I did hear some ticking going on in there when I bought the vehicle, though the ticking stopped, so I drove on. It does have a fairly new distributor, so maybe it wasn’t put in correctly and wore out the sensor ??? I have a friend coming over with a quality scan tool that might be able to tell me more. I have a simple WiFi code reader and an iPhone app.
I dislike continuing to change expensive parts with no effect.
How else would I check the ignition, to rule that out?
Thanks for the quick response.
Brian
I dislike continuing to change expensive parts with no effect.
How else would I check the ignition, to rule that out?
Thanks for the quick response.
Brian
Last edited by Brianelferdnk; 03-06-2018 at 11:47 AM.
03-06-2018, 01:36 PM
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Two things operate the "control" side of the ASD relay. The positive is provided by the ignition switch, and the ground is provided by the PCM. If the ground is what is dropping out then it is most likely because the PCM is choosing to disable the ignition for some reason (failure to read engine position would be one valid reason, security system after battery disconnect could be another, etc.). If the positive is dropping out, that would be a failing ignition switch, but it would be very unusual for that to happen consistently (every time, after a few seconds).
Do you have a factory security system?
Do you have a factory security system?
03-06-2018, 02:11 PM
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Hahaha. Factory security system....... This is a 96 Cherokee sport, manual transmission, door locks, windows, mirrors. Etc. I guess it’s possible, but I do not belive I have a factory or aftermarket security system. I’ll explore that as well though. I’m going to check the ignition signal now. I’m pretty sure it is the pcm disconnecting the ASD, but it never hurts to check. I’m just hoping it’s not the pcm. I ordered a cam sensor pickup coil. It will be here tomorrow. I haven’t heard from my friend with the meter, but I’ll let you know what I find out.
Thnaks again.
Thnaks again.
03-06-2018, 09:38 PM
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Hahaha. Factory security system....... This is a 96 Cherokee sport, manual transmission, door locks, windows, mirrors. Etc. I guess it’s possible, but I do not belive I have a factory or aftermarket security system. I’ll explore that as well though. I’m going to check the ignition signal now. I’m pretty sure it is the pcm disconnecting the ASD, but it never hurts to check. I’m just hoping it’s not the pcm. I ordered a cam sensor pickup coil. It will be here tomorrow. I haven’t heard from my friend with the meter, but I’ll let you know what I find out.
Thnaks again.
Thnaks again.
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03-08-2018, 11:20 AM
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Still no joy. Did some more testing and replacing. Replaced the cam position sensor in the distributor, no change. Tested the ignition positive at the ASD relay and it’s good. Tested the negative from the PCM to the ASD RELAY and it is good until I put the relay back in,then it trips off. It does this with known good relays. So it’s some sensor/fault/short, down stream of the ASD relay that when powered is telling the pcm to shut off the ASD.
I did a little test with my new and old crank position sensor. If I unplug the CPS and turn on the ignition, when I plug the Crank PositionSensor back in, the ASD relay cycles on, the about one second to off. Unplug it with no change, plug it back in and it cycles the relay again. Does this sound like a new bad CPS. I took the old cps, with the ignition on and plugged it in. When I touch something grounded with the sensor, it cycles the ASD on and back off. Removing the CPS from the ground and putting it back near the ground Cycles the ASD again.
I really wish wish I had a good scan tool. My OSB reader is showing no faults
What other sensors downstream of the ASD could be telling the pcm to shut off the ASD?
I did a little test with my new and old crank position sensor. If I unplug the CPS and turn on the ignition, when I plug the Crank PositionSensor back in, the ASD relay cycles on, the about one second to off. Unplug it with no change, plug it back in and it cycles the relay again. Does this sound like a new bad CPS. I took the old cps, with the ignition on and plugged it in. When I touch something grounded with the sensor, it cycles the ASD on and back off. Removing the CPS from the ground and putting it back near the ground Cycles the ASD again.
I really wish wish I had a good scan tool. My OSB reader is showing no faults
What other sensors downstream of the ASD could be telling the pcm to shut off the ASD?
03-08-2018, 03:46 PM
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Got it
So, I pulled the ignition coil, and did an ohm test and came out with 6000 ohms between the 2 plug pins, plus it was cracked. I threw another one in and It started up. Rough, I guess just learning all the new parts I put in, but it’s perfect now. Bad ignition coil.
I learned that the ASD cycles for 2 seconds on ignition to prime the fuel pump and test the sensors, then cycles off until cranking the engine, so testing the positive side of the coil plug didn’t work for me since the relay cycled. My voltmeter is digital, so takes a second to respond. I therefor thought no power was getting to the coil during cranking. Thanks to all that helped.
The easiest thing to replace was the culprit,(coil). At least now it has new crank position and cam sensors. 🙄😁
I learned that the ASD cycles for 2 seconds on ignition to prime the fuel pump and test the sensors, then cycles off until cranking the engine, so testing the positive side of the coil plug didn’t work for me since the relay cycled. My voltmeter is digital, so takes a second to respond. I therefor thought no power was getting to the coil during cranking. Thanks to all that helped.
The easiest thing to replace was the culprit,(coil). At least now it has new crank position and cam sensors. 🙄😁
05-21-2019, 05:02 AM
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96 Cherokee no power to the coil
I had the same problem replace all kinds of things under the hood still had no power going to the coil decided to pull every fuse and check them personally found out number 20 fuse what's blowing every time I turned on the key can I figure out what it was then I got to wire schematics chart and started chasing wires looking for a short
What happened and I found out his comment on these the rear oxygen sensor bracket rusted out breaking leaving the the wires to fall into the driveshaft and rub through and short out once I did that fix that was a cheap fixed
What happened and I found out his comment on these the rear oxygen sensor bracket rusted out breaking leaving the the wires to fall into the driveshaft and rub through and short out once I did that fix that was a cheap fixed
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