Renix Disaster
06-30-2017, 04:17 PM
#1
Junior Member
Thread Starter
Join Date: Aug 2013
Location: Petaluma CA
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1988
Model: Cherokee
Engine: 4.0
Renix Disaster
Hello everyone.
I am at my wits end with this one. the issue is and has been no spark for the longest time. I have replaced the entire ignition system, some parts twice. If there is anyone with another idea I will try it, mostly because I am out of ideas.
It all started with the Jeep (1988 Cherokee 4.0) shutting off while I was driving. I turned the key off and restarted the jeep and it shut off moments later. I was less than a half mile from home and was able to limp home and got it in the garage.
When I took a look at it I found a no spark situation at the plugs. I traced it back to the ICM (ignition control module). on the ICM I had a good ground, positive 12v and a five volt AC voltage (found out later that it was supposed to be a DC square wave signal.
Eventually I was able to trace the bad signal back to the computer which appears to have the correct inputs: 12v battery, 12v acc, .5 volt CPS and 5v from sync sensor. I wont go into detail of all the easter egging I have done and just list all of the parts I have replaced.
ICM
coil
plugs
wires
cap
rotor
distributor w/ sync sensor
cps
remove C101
ECM x2
ignition switch
Any ideas on where to go next will be appreciated.
I am at my wits end with this one. the issue is and has been no spark for the longest time. I have replaced the entire ignition system, some parts twice. If there is anyone with another idea I will try it, mostly because I am out of ideas.
It all started with the Jeep (1988 Cherokee 4.0) shutting off while I was driving. I turned the key off and restarted the jeep and it shut off moments later. I was less than a half mile from home and was able to limp home and got it in the garage.
When I took a look at it I found a no spark situation at the plugs. I traced it back to the ICM (ignition control module). on the ICM I had a good ground, positive 12v and a five volt AC voltage (found out later that it was supposed to be a DC square wave signal.
Eventually I was able to trace the bad signal back to the computer which appears to have the correct inputs: 12v battery, 12v acc, .5 volt CPS and 5v from sync sensor. I wont go into detail of all the easter egging I have done and just list all of the parts I have replaced.
ICM
coil
plugs
wires
cap
rotor
distributor w/ sync sensor
cps
remove C101
ECM x2
ignition switch
Any ideas on where to go next will be appreciated.
Last edited by Cjjcalhoun; 06-30-2017 at 11:49 PM.
06-30-2017, 06:39 PM
#2
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,876
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
06-30-2017, 09:23 PM
#4
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,876
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Possibly.
but there are better places to begin.
but there are better places to begin.
06-30-2017, 09:28 PM
#5
Junior Member
Join Date: Aug 2014
Location: Virginia
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1999
Model: Cherokee
Engine: 4.0L
I would start with the crank sensor. They are cheap, easy, know to fail, and will cause your problem. I had a similar situation with my 89 Laredo. Let me know what you find.
06-30-2017, 09:31 PM
#6
CF Veteran
Join Date: Apr 2016
Location: Pasquotank, NC
Posts: 1,679
Likes: 0
Received 15 Likes
on
13 Posts
Year: 1990
Model: Cherokee
Engine: 4.0
I would follow whatever instruction Cruiser provides. He was working the dealerships when the Renix jeeps were new. He has helped me sort my 90 out a couple times. Very knowledgeable.
Trending Topics
06-30-2017, 11:48 PM
#8
Junior Member
Thread Starter
Join Date: Aug 2013
Location: Petaluma CA
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1988
Model: Cherokee
Engine: 4.0
Thank's Cruiser. I will try those tomorrow.
The crankshaft position sensor is a good .5 volts at the pin going into the ECM.
Cruiser, do you know what you should see out of the sync sensor? My latest change was the distrubitor because I was getting a solid 5v DC out of it and I read that it should be a 5v square wave.
The crankshaft position sensor is a good .5 volts at the pin going into the ECM.
Cruiser, do you know what you should see out of the sync sensor? My latest change was the distrubitor because I was getting a solid 5v DC out of it and I read that it should be a 5v square wave.
07-01-2017, 12:18 AM
#9
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,876
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Thank's Cruiser. I will try those tomorrow.
The crankshaft position sensor is a good .5 volts at the pin going into the ECM.
Cruiser, do you know what you should see out of the sync sensor? My latest change was the distrubitor because I was getting a solid 5v DC out of it and I read that it should be a 5v square wave.
The crankshaft position sensor is a good .5 volts at the pin going into the ECM.
Cruiser, do you know what you should see out of the sync sensor? My latest change was the distrubitor because I was getting a solid 5v DC out of it and I read that it should be a 5v square wave.
07-01-2017, 12:33 AM
#11
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,876
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
07-01-2017, 12:46 AM
#13
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,876
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
07-01-2017, 08:06 AM
#14
Senior Member
I know Cruiser is helping you so I'll just chime in to make sure you don't overlook the simple stuff like grounding and connectors. I had a problem with the engine dying and it was traced to the dipstick ground that would go open when the engine was warmed up. I'd refresh all the connectors on the wiring on the distributor side (right side) of the engine.
Also, just to nit-pick, when you are saying "no-start" do you mean it doesn't engage the starter when you turn the key or that the starter turns but the engine won't run? I saw you replaced the ignition key so that made me wonder what we're talking about.
Also, just to nit-pick, when you are saying "no-start" do you mean it doesn't engage the starter when you turn the key or that the starter turns but the engine won't run? I saw you replaced the ignition key so that made me wonder what we're talking about.
07-01-2017, 08:09 AM
#15
::CF Moderator::
Join Date: Aug 2011
Location: Prescott, Az
Posts: 43,876
Received 1,526 Likes
on
1,238 Posts
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
I know Cruiser is helping you so I'll just chime in to make sure you don't overlook the simple stuff like grounding and connectors. I had a problem with the engine dying and it was traced to the dipstick ground that would go open when the engine was warmed up. I'd refresh all the connectors on the wiring on the distributor side (right side) of the engine.
Also, just to nit-pick, when you are saying "no-start" do you mean it doesn't engage the starter when you turn the key or that the starter turns but the engine won't run? I saw you replaced the ignition key so that made me wonder what we're talking about.
Also, just to nit-pick, when you are saying "no-start" do you mean it doesn't engage the starter when you turn the key or that the starter turns but the engine won't run? I saw you replaced the ignition key so that made me wonder what we're talking about.