Cranks but wont start! Backfires! Not CPS!
11-09-2019, 02:10 PM
#1
Newbie
Thread Starter
Join Date: Nov 2019
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee (XJ)
Cranks but wont start! Backfires! Not CPS!
Good afternoon all. I'm a noob here. I'm praying someone here can help me. My fiance has a RHD 98 mail jeep. It's been been a piece of work due to the previous owner and I've been able to search here and figure it out until now.
She was driving down the road and heard a "pop" then it died. Wouldn't start. Went and trailed it home and dug in. Tested the CPS as it was my preliminary culprit. It reads fine.
Checked for spark at the coil and I got it. Have spark at all 6 cylinders spark plugs.
Replaced the cap and rotor and plugs.
About a month back I replaced the TPS. It had and still has code P0122. Replacing it didnt make it go away. But it checks out fine. I also jumped the signal and constant 12v to check for a short in the system and nothing.
It cranks and cranks and cranks but will not start. Occasionally, randomly, when you let off the key it will pop a puff of smoke through the throttle body. (I have the intake off).
I have 4 codes currently. But they've been since before this.
P0443
P0122
P0705
P1694
I'm at my end of ideas here. Hoping someone can shed some light as to what I'm missing.
She was driving down the road and heard a "pop" then it died. Wouldn't start. Went and trailed it home and dug in. Tested the CPS as it was my preliminary culprit. It reads fine.
Checked for spark at the coil and I got it. Have spark at all 6 cylinders spark plugs.
Replaced the cap and rotor and plugs.
About a month back I replaced the TPS. It had and still has code P0122. Replacing it didnt make it go away. But it checks out fine. I also jumped the signal and constant 12v to check for a short in the system and nothing.
It cranks and cranks and cranks but will not start. Occasionally, randomly, when you let off the key it will pop a puff of smoke through the throttle body. (I have the intake off).
I have 4 codes currently. But they've been since before this.
P0443
P0122
P0705
P1694
I'm at my end of ideas here. Hoping someone can shed some light as to what I'm missing.
11-09-2019, 04:36 PM
#3
Newbie
Thread Starter
Join Date: Nov 2019
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee (XJ)
11-09-2019, 06:11 PM
#4
Banned
Not too long ago earlier this year I was participating in a thread.. The complaint was similar to what you have going on with your Jeep.
You say you had a backfire out the intake. The other guy said the same thing. His would just crank and crank... Even once all of a sudden he said it backfired out the intake so hard it blew out his airbox. His issue was a bad cam position sensor.
This has to be timing related, right?
(edited to add):
If it is igniting to backfire out the intake.. It has to be timing related, right?
You say you had a backfire out the intake. The other guy said the same thing. His would just crank and crank... Even once all of a sudden he said it backfired out the intake so hard it blew out his airbox. His issue was a bad cam position sensor.
This has to be timing related, right?
(edited to add):
If it is igniting to backfire out the intake.. It has to be timing related, right?
Last edited by Noah911; 11-09-2019 at 06:43 PM.
11-10-2019, 03:44 AM
#5
Seasoned Member
Join Date: Sep 2019
Location: Around the world
Posts: 328
Likes: 0
Received 92 Likes
on
77 Posts
Year: 2001 / 1999
Model: Cherokee (XJ)
Engine: Fire breathing 4 point Oh!!!
Have you checked fuel pressure?
Are you able to rent some NOID lights to check injector pulse?
Compression test in all the cylinders?
Are you able to check for codes / view live data with a scanner?
Did you use Mopar original sensors, when you replaced the TPS?
Did you ever figure out what the "pop" was, that caused it to die?
Are you able to rent some NOID lights to check injector pulse?
Compression test in all the cylinders?
Are you able to check for codes / view live data with a scanner?
Did you use Mopar original sensors, when you replaced the TPS?
Did you ever figure out what the "pop" was, that caused it to die?
11-10-2019, 10:01 AM
#6
Member
From the experience i have had with the only car backfiring through the intake was a pluged cat. Wouldnt fire at all even with starting fluid, just kept poping out the intake. Finally disconnected the down pipe and it fired right up first try. Might want to pull the down pipe and give it a shot. A cat is easy to gut tell you get a new one
Trending Topics
11-10-2019, 11:28 AM
#8
Newbie
Thread Starter
Join Date: Nov 2019
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee (XJ)
Have you checked fuel pressure?
I have pressure, but I have not checked with a gauge.
Are you able to rent some NOID lights to check injector pulse?
I can borrow a set. I haven't yet because all 6 plugs were flooded with gas so I assumed sage to say Injectors are firing.
Compression test in all the cylinders?
I haven't yet but can. Not sure what that would tell me though.
Are you able to check for codes / view live data with a scanner?
Not a live data scanner. Unfortunately not that fancy. However after this issue. It is next on my list.
Did you use Mopar original sensors, when you replaced the TPS?
No. BWD. Only thing local had. CPS and TPS are BWD. but, both check out fine when I measure them.
Did you ever figure out what the "pop" was, that caused it to die?
I have pressure, but I have not checked with a gauge.
Are you able to rent some NOID lights to check injector pulse?
I can borrow a set. I haven't yet because all 6 plugs were flooded with gas so I assumed sage to say Injectors are firing.
Compression test in all the cylinders?
I haven't yet but can. Not sure what that would tell me though.
Are you able to check for codes / view live data with a scanner?
Not a live data scanner. Unfortunately not that fancy. However after this issue. It is next on my list.
Did you use Mopar original sensors, when you replaced the TPS?
No. BWD. Only thing local had. CPS and TPS are BWD. but, both check out fine when I measure them.
Did you ever figure out what the "pop" was, that caused it to die?
11-10-2019, 11:58 AM
#9
Banned
As a camshaft position sensor starts having problems and weakens, the transmitted signal to the car’s computer weakens as well. This means eventually the signal can be so weak that it will not allow the car to start since there may be no spark from the ignition.
It sounds like you have a bunch of unburnt fuel remaining in the cylinders because they are not being fired off by adequate spark, correctly timed, or even at all...
Do you see spark, or adequate spark happening.. as it is cranking and not firing off?
If you've tested the CRANK sensor and it is fine? It sounds like a bad failing CAM sensor to me.
It sounds like you have a bunch of unburnt fuel remaining in the cylinders because they are not being fired off by adequate spark, correctly timed, or even at all...
Do you see spark, or adequate spark happening.. as it is cranking and not firing off?
If you've tested the CRANK sensor and it is fine? It sounds like a bad failing CAM sensor to me.
11-10-2019, 03:35 PM
#11
Newbie
Thread Starter
Join Date: Nov 2019
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee (XJ)
As a camshaft position sensor starts having problems and weakens, the transmitted signal to the car’s computer weakens as well. This means eventually the signal can be so weak that it will not allow the car to start since there may be no spark from the ignition.
It sounds like you have a bunch of unburnt fuel remaining in the cylinders because they are not being fired off by adequate spark, correctly timed, or even at all...
Do you see spark, or adequate spark happening.. as it is cranking and not firing off?
If you've tested the CRANK sensor and it is fine? It sounds like a bad failing CAM sensor to me.
It sounds like you have a bunch of unburnt fuel remaining in the cylinders because they are not being fired off by adequate spark, correctly timed, or even at all...
Do you see spark, or adequate spark happening.. as it is cranking and not firing off?
If you've tested the CRANK sensor and it is fine? It sounds like a bad failing CAM sensor to me.
11-10-2019, 03:36 PM
#12
Newbie
Thread Starter
Join Date: Nov 2019
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee (XJ)
Also I read I wouldn't have spark, which I do.
11-10-2019, 04:09 PM
#13
CF Veteran
I'd pull the valve cover and the timing cover and take a look see. While it's extremely rare to jump a timing chain if the gears are in decent shape, plenty of other catastrophic events can happen.
Check out this guys experience:
https://www.jeepforum.com/forum/f310...teeth-3032833/
Will avoid mentioning the Hantek...
11-12-2019, 07:26 AM
#15
Newbie
Thread Starter
Join Date: Nov 2019
Posts: 7
Likes: 0
Received 0 Likes
on
0 Posts
Model: Cherokee (XJ)
I appreciate all the help. But I was able to self diagnose and fix it. A piece of advice. When I'm working on a new vehicle I have a white board and I write down everything I see wrong. Relevant to the issue or not. So I can make a plan. When testing for spark off the coil i thought it seemed "faint" but i had spark. And the battery was down to 10 volts so I didnt think anymore if it. So I grabbed a spare coil to go out and try it. And nothing. But then I noticed something. The wire terminals in the plug have a green rubber insulator. I could see them. I unplugged it and looked inside, and the connector had back out. I held them in by hand and held the coil in hand and had my dad start it. BOOM! Fired right up. So I put the connector back in the bolted in coil and pushed hard. It started. But I began tapping it with a small screwdriver to simulate rosd vibration. And it popped from backfiring the sunburnt fuel because it was losing spark and shut off.
I've since ordered a new connector from rock auto. Will be here tomorrow. Gonna solder the wires on, heat shrink and loom them and get this thing out of my garage taking up precise mustang space.
I appreciate everyone's attempts at help!!!
I've since ordered a new connector from rock auto. Will be here tomorrow. Gonna solder the wires on, heat shrink and loom them and get this thing out of my garage taking up precise mustang space.
I appreciate everyone's attempts at help!!!