jeep xj no start, weak spark
11-23-2020, 09:38 PM
#1
Newbie
Thread Starter
Join Date: Nov 2020
Location: Nottingham NH
Posts: 12
Likes: 0
Received 1 Like
on
1 Post
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
jeep xj no start, weak spark
I’m at a complete loss here, I had a problem with my 1999 jeep cherokee classic where it wouldn’t start this week. it has fuel pressure, and injectors are delivering fuel. the spark is a yellow/orange color which means it’s weak. correct? so I installed a new coil and it started up, but barely. It would start and would continually try to stall out at idle, so i went on and replaced the distributor and spark plugs and now won’t fire what so ever. Did I install the distributor wrong? I was pretty confident that i had the timing set properly. Or is there something else i’m missing here? Is it possible it’s a bad pcm?
Last edited by jacobsicard; 11-23-2020 at 10:20 PM.
11-23-2020, 10:33 PM
#2
CF Veteran
Join Date: May 2012
Location: Lost in the wilds of Virginia
Posts: 7,964
Received 956 Likes
on
771 Posts
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Welcome to the forum. 
Correct.
Probably. 
Never assume. Double check yourself, and do NOT use any info that comes from Chilton or Haynes. They are often wrong.
Yes, it's theoretically possible, but that's a long way down the list of possibles.
Check the basics: How are your cables? Grounds? A bad ground here and there can wreak havoc on many systems. This is especially true with our XJs because most of the engine functions get constant 12v, and then the PCM provides ground to fire the device (coil, injectors, etc.). A marginal PCM ground will cause lots of grief.
The PCM grounds to a plate near the distributor, and your main battery cable grounds there, too.
Never assume. Double check yourself, and do NOT use any info that comes from Chilton or Haynes. They are often wrong.Yes, it's theoretically possible, but that's a long way down the list of possibles.
Check the basics: How are your cables? Grounds? A bad ground here and there can wreak havoc on many systems. This is especially true with our XJs because most of the engine functions get constant 12v, and then the PCM provides ground to fire the device (coil, injectors, etc.). A marginal PCM ground will cause lots of grief.
The PCM grounds to a plate near the distributor, and your main battery cable grounds there, too.
11-24-2020, 12:12 PM
#3
Newbie
Thread Starter
Join Date: Nov 2020
Location: Nottingham NH
Posts: 12
Likes: 0
Received 1 Like
on
1 Post
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
Welcome to the forum.
Correct.
Probably. Never assume. Double check yourself, and do NOT use any info that comes from Chilton or Haynes. They are often wrong.
Yes, it's theoretically possible, but that's a long way down the list of possibles.
Check the basics: How are your cables? Grounds? A bad ground here and there can wreak havoc on many systems. This is especially true with our XJs because most of the engine functions get constant 12v, and then the PCM provides ground to fire the device (coil, injectors, etc.). A marginal PCM ground will cause lots of grief.
The PCM grounds to a plate near the distributor, and your main battery cable grounds there, too.
Correct.
Probably.
Never assume. Double check yourself, and do NOT use any info that comes from Chilton or Haynes. They are often wrong.Yes, it's theoretically possible, but that's a long way down the list of possibles.
Check the basics: How are your cables? Grounds? A bad ground here and there can wreak havoc on many systems. This is especially true with our XJs because most of the engine functions get constant 12v, and then the PCM provides ground to fire the device (coil, injectors, etc.). A marginal PCM ground will cause lots of grief.
The PCM grounds to a plate near the distributor, and your main battery cable grounds there, too.
I checked the grounds and they seemed good, is it possible that a bad CPS would cause a weak spark?
11-24-2020, 07:40 PM
#4
Newbie
Thread Starter
Join Date: Nov 2020
Location: Nottingham NH
Posts: 12
Likes: 0
Received 1 Like
on
1 Post
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
Update: Replaced the CPS and checked the grounds, still nothing. I do have power getting to the coil, had 11.5 volts and the battery was at 12.06V. So I did new spark plug wires and tried another new coil. Nothing did the trick, still cranks with no fire, even with starting fluid so i know it’s not a fuel issue.
11-24-2020, 10:07 PM
#5
CF Veteran
Join Date: May 2012
Location: Lost in the wilds of Virginia
Posts: 7,964
Received 956 Likes
on
771 Posts
Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
CPS won't give a weak spark.
How did you check your grounds? IF you didn't take them apart, you didn't check them.
How did you check your grounds? IF you didn't take them apart, you didn't check them.
Trending Topics
11-25-2020, 10:27 AM
#9
CF Veteran
11-25-2020, 11:11 AM
#10
Newbie
Thread Starter
Join Date: Nov 2020
Location: Nottingham NH
Posts: 12
Likes: 0
Received 1 Like
on
1 Post
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
11-25-2020, 11:33 AM
#11
CF Veteran
Join Date: Aug 2019
Location: Littleton, CO
Posts: 1,450
Received 260 Likes
on
201 Posts
Year: '96
Model: Cherokee (XJ)
Engine: 4.0 HO
If the grounds are good and clean the new CPS didn't fix it, then I'd have to say its the part that provides the voltage for the spark. Battery or alternator? If you have a battery charger, hook that up and see if it helps to start the engine, or just an old school jump start from another vehicle. If it starts up much easier, check your battery and alternator cables for signs of bad stuff, loose connections, etc....
11-25-2020, 11:42 AM
#12
Newbie
Thread Starter
Join Date: Nov 2020
Location: Nottingham NH
Posts: 12
Likes: 0
Received 1 Like
on
1 Post
Year: 1999
Model: Cherokee (XJ)
Engine: 4.0L
If the grounds are good and clean the new CPS didn't fix it, then I'd have to say its the part that provides the voltage for the spark. Battery or alternator? If you have a battery charger, hook that up and see if it helps to start the engine, or just an old school jump start from another vehicle. If it starts up much easier, check your battery and alternator cables for signs of bad stuff, loose connections, etc....
11-25-2020, 12:13 PM
#15
CF Veteran
Join Date: Aug 2019
Location: Littleton, CO
Posts: 1,450
Received 260 Likes
on
201 Posts
Year: '96
Model: Cherokee (XJ)
Engine: 4.0 HO
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?