Oh yes.. more starting problems
Thread Starter
Seasoned Member
Joined: Jan 2009
Posts: 345
Likes: 1
Year: 1989
Model: Cherokee
Engine: inline 6 4.0L
Oh yes.. more starting problems
I've been away from my jeep for about 2 months now, but I am finally back. When I got into my jeep it started right up, and ran fine all last week. On friday it my heep decided it didn't like to start anymore.
The engine turns, fuel is getting to the rail, air is getting to the cylinders, only thing missing is SPARK. The ignition coil will not send a spark to the distributor!
we've done every test I could find on the coil, as well as tests on the cps, and they looked fine.
We also checked all of the wires heading to the ignition control module and they have power going to them.
CPS is the only thing I can possibly think of, but I replaced it about 5 months ago.
I'm getting sick of this thing costing me so much money, and am actually considering getting rid of it.
Please
me
The engine turns, fuel is getting to the rail, air is getting to the cylinders, only thing missing is SPARK. The ignition coil will not send a spark to the distributor!
we've done every test I could find on the coil, as well as tests on the cps, and they looked fine.
We also checked all of the wires heading to the ignition control module and they have power going to them.
CPS is the only thing I can possibly think of, but I replaced it about 5 months ago.
I'm getting sick of this thing costing me so much money, and am actually considering getting rid of it.
Please
me
CF Veteran
Joined: Apr 2008
Posts: 13,952
Likes: 17
Model: Cherokee
From the 88FSM (Close enough to the 89)
Want the entire FSM? Okie-Dokie!
http://www.greatlakesxj.com/tech.html
The ECU provides an input signal to the ICM. The ICM has only
two outputs:
* Tach signal to the tachometer and diagnostic connector
* High voltage from the coil to the distributor cap.
Electrical feed to the ICM is through terminal "A" of
Connector No. 1 on the module. See Fig. 3.
NOTE: Electrical supply only occurs with the ignition switch in
the START and RUN position.
Terminal "B" of Connector No. 1 is grounded at the engine oil
dipstick bracket along with the ECU ground wire and Oxygen (O2) sensor
ground.
The tachometer output signal wire of the ICM is connected to
Pin No. 1 of the "D1" Diagnostic connector. The wire is routed to the
diagnostic connector through a short section of the ECU harness, the
engine, and the instrument panel harness. This type of routing
eliminates any potential electrical interference from occurring in the
various ECU circuitry.
Ignition firing signals from ECU terminal "27" are
transmitted through terminal "B" of Connector No. 2 on the ICM. the
ignition signal from the ECU is received by the ICM in the form of a 5
volt square wave. As the leading edge of the wave contacts the
ignition circuitry in the ICM, the ICM charges the coil primary
windings.
When coil saturation occurs, the module circuitry opens the
primary windings to collapse the magnetic field in the windings. This
induces the coil secondary windings which is then transmitted to the
spark plug via the coil wire, distributor cap, and rotor.
two outputs:
* Tach signal to the tachometer and diagnostic connector
* High voltage from the coil to the distributor cap.
Electrical feed to the ICM is through terminal "A" of
Connector No. 1 on the module. See Fig. 3.
NOTE: Electrical supply only occurs with the ignition switch in
the START and RUN position.
Terminal "B" of Connector No. 1 is grounded at the engine oil
dipstick bracket along with the ECU ground wire and Oxygen (O2) sensor
ground.
The tachometer output signal wire of the ICM is connected to
Pin No. 1 of the "D1" Diagnostic connector. The wire is routed to the
diagnostic connector through a short section of the ECU harness, the
engine, and the instrument panel harness. This type of routing
eliminates any potential electrical interference from occurring in the
various ECU circuitry.
Ignition firing signals from ECU terminal "27" are
transmitted through terminal "B" of Connector No. 2 on the ICM. the
ignition signal from the ECU is received by the ICM in the form of a 5
volt square wave. As the leading edge of the wave contacts the
ignition circuitry in the ICM, the ICM charges the coil primary
windings.
When coil saturation occurs, the module circuitry opens the
primary windings to collapse the magnetic field in the windings. This
induces the coil secondary windings which is then transmitted to the
spark plug via the coil wire, distributor cap, and rotor.
http://www.greatlakesxj.com/tech.html
CF Veteran
Joined: Jul 2009
Posts: 2,158
Likes: 11
From: Chico,ca
Year: 89
Model: Cherokee
Engine: 4.0
I will share what has happened to me,just taking my son to school one day mine died,it came down to the icm under the coil,I changed it out and it ran fine,I have spares I carry,I have also had it happen due to the coil. They are easy to test if you have volt meter and a manual. I have never had the cps go out on me,but you can check it by using a volt meter and making sure there is no resistance,and by checking voltage to and from it should be about 3.5-5.
When you turn your key on there should be 12 volts going to your icm,if not trace it back to the ignition.
When you turn your key on there should be 12 volts going to your icm,if not trace it back to the ignition.
Thread Starter
Seasoned Member
Joined: Jan 2009
Posts: 345
Likes: 1
Year: 1989
Model: Cherokee
Engine: inline 6 4.0L
Thanks. How much would an ICM set me back??
Its weird how the problem started. One day I went out to go somewhere, and it just wouldn't fire, and then the next day I tried it again and it worked. Then for the next 2-3 days, It would be random whether it would fire or not, and when it wouldn't I would unplug the cps and the spark wire from the coil, and it would start after a little bit.
This tells me that the cps is bad, but tests show that it is not.
We thought it was the icm as well, so we might look into that.
Its weird how the problem started. One day I went out to go somewhere, and it just wouldn't fire, and then the next day I tried it again and it worked. Then for the next 2-3 days, It would be random whether it would fire or not, and when it wouldn't I would unplug the cps and the spark wire from the coil, and it would start after a little bit.
This tells me that the cps is bad, but tests show that it is not.
We thought it was the icm as well, so we might look into that.
Trending Topics
Thread Starter
Seasoned Member
Joined: Jan 2009
Posts: 345
Likes: 1
Year: 1989
Model: Cherokee
Engine: inline 6 4.0L
http://www.pirate4x4.com/tech/billav...ion_manual.pdf
This has been very helpful to me, and the cps is on pg 16, and the check on pg 17. I tested the one in the jeep, and got 234 ohms, tested the old one and got 236, and then tested a brand new one and got 237, so there seems to be nothing wrong with it. I have arranged to take it into the dealer next thursday, but am hoping to solve the problem before that, becuase they're going to charge me a fortune. (The jeep was taken into the dealer for a diagnostics reading 2 weeks before the problem came up, and charged me $50 to tell me there was nothing wrong with it). GOD just called parts store they want $200 for the stupid ICM!!!
This has been very helpful to me, and the cps is on pg 16, and the check on pg 17. I tested the one in the jeep, and got 234 ohms, tested the old one and got 236, and then tested a brand new one and got 237, so there seems to be nothing wrong with it. I have arranged to take it into the dealer next thursday, but am hoping to solve the problem before that, becuase they're going to charge me a fortune. (The jeep was taken into the dealer for a diagnostics reading 2 weeks before the problem came up, and charged me $50 to tell me there was nothing wrong with it). GOD just called parts store they want $200 for the stupid ICM!!!
Thread
Thread Starter
Forum
Replies
Last Post
seansr
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
13
Oct 20, 2025 02:48 PM
Jose Calderon
Stock Grand Cherokee Tech. All ZJ/WJ/WK Non-modified/stock questions go here!
17
Sep 17, 2015 08:57 PM
DanO55
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
1
Aug 28, 2015 07:16 PM
petejeep95
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
4
Aug 22, 2015 11:39 AM
CCKen
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
3
Aug 20, 2015 08:07 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)