jeep xj no start, weak spark
#16
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Location: Nottingham NH
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Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
Possible. Odds arent great, but its possible. I want to say that the distributor cap CAN go on wrong, but if it had this issue before you replaced that, its probably not the issue, unless it had moved by itself before you replaced it and put the new one on in the same orientation as you took it off.
Did you replace the rotor with the cap?
Did you replace the rotor with the cap?
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RockyMtn96XJ (11-25-2020)
#17
CF Veteran
With key on, slowly turn the engine over by hand while probing the signal wires for the CkPS and CPS. You should see a 5.0 VDC signal.
#18
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If you are getting signals, the next thing to do is see if the signals are synced. CkPS (blue) and CPS (coil sync) should be doing this:
This we gotta figure out how you're gonna do...
This we gotta figure out how you're gonna do...
#20
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Year: '96
Model: Cherokee (XJ)
Engine: 4.0 HO
Is there a way to have 2 multimeters going at the same time and listen for the beeps or watch the voltages come and go to see if they're in sync? Would be harder that way, but it could help...
#21
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An entry level Hantek like this one is only 90 bucks, so if you consider that vs feeding the parts cannon, could turn out to be a pretty good deal.
#22
CF Veteran
BTW do you have an FSM? This is 1997 so should closely cover yours:
https://cdn.xjjeeps.com/pdf/en-us/19...ice-manual.pdf
Check out page 8D-6. Also test throttle position sensor. Your spark and fuel testing suggest the CkPS/CPS sync (or perhaps a wire or connector is broken so the signals aren't getting to the PCM) is the culprit but if not...
https://cdn.xjjeeps.com/pdf/en-us/19...ice-manual.pdf
Check out page 8D-6. Also test throttle position sensor. Your spark and fuel testing suggest the CkPS/CPS sync (or perhaps a wire or connector is broken so the signals aren't getting to the PCM) is the culprit but if not...
#23
CF Veteran
As an aside, a cam/crank that is out of phase would look something like
https://www.jeepforum.com/forum/f19/...e-fix-3487474/
While all this looks pretty flashy, these examples are from COP ignitions (me and the above poster have 2000s). I think the coil sync works the same, they just took the sync out of the distributor in 2000.
https://www.jeepforum.com/forum/f19/...e-fix-3487474/
While all this looks pretty flashy, these examples are from COP ignitions (me and the above poster have 2000s). I think the coil sync works the same, they just took the sync out of the distributor in 2000.
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#27
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Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
so i decided to check fuel since i have gone through almost the entire ignition system, turns out my fuel pressure was very low🤦🏻♂️ doesn’t explain the yellow spark but i’ll see if it runs with a new fuel pump
#28
Senior Member
You might want to have your battery checked instead of replacing the fuel pump. I found that my 99 when the battery is low would turn over slowly and then fire up only to die within seconds if I did not tease it with the throttle. Once it was running for a couple of minutes, the rpms was about 700 and the alternator was producing voltage it would stay running on its on. My theory is that it did not have enough voltage to operate the fuel pump properly at the correct pressure. If not why wouldn't it stay running without me feathering the throttle?
The reason my battery was drained was I had the hood up and the door open checking the fog lamp switch sometimes with the key on, as well.
It was able to boost off with a LiOn booster pack (about the size of a pack of cigs), but I will have the battery tested today. I am almost sure its time for a new one as this one is old and tired. A cold snap would send it down for good, I am afraid.
Good Luck and get her back on the road!
The reason my battery was drained was I had the hood up and the door open checking the fog lamp switch sometimes with the key on, as well.
It was able to boost off with a LiOn booster pack (about the size of a pack of cigs), but I will have the battery tested today. I am almost sure its time for a new one as this one is old and tired. A cold snap would send it down for good, I am afraid.
Good Luck and get her back on the road!
#29
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Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
You might want to have your battery checked instead of replacing the fuel pump. I found that my 99 when the battery is low would turn over slowly and then fire up only to die within seconds if I did not tease it with the throttle. Once it was running for a couple of minutes, the rpms was about 700 and the alternator was producing voltage it would stay running on its on. My theory is that it did not have enough voltage to operate the fuel pump properly at the correct pressure. If not why wouldn't it stay running without me feathering the throttle?
The reason my battery was drained was I had the hood up and the door open checking the fog lamp switch sometimes with the key on, as well.
It was able to boost off with a LiOn booster pack (about the size of a pack of cigs), but I will have the battery tested today. I am almost sure its time for a new one as this one is old and tired. A cold snap would send it down for good, I am afraid.
Good Luck and get her back on the road!
The reason my battery was drained was I had the hood up and the door open checking the fog lamp switch sometimes with the key on, as well.
It was able to boost off with a LiOn booster pack (about the size of a pack of cigs), but I will have the battery tested today. I am almost sure its time for a new one as this one is old and tired. A cold snap would send it down for good, I am afraid.
Good Luck and get her back on the road!