No Spark after CTS replacement -
LinkBack Thread Tools
post #1 of 3 Old 04-08-2011, 01:47 AM Thread Starter
Registered User
1995 ZJ 
Join Date: Apr 2011
Location: Bangor
Posts: 41
No Spark after CTS replacement

Does the '95 Laredo (6 cylinder, 2 wheel drive) have a separate coolant temperature sender (not sensor) to the dashboard gauge?

Long story: After tune up in October at national chain auto center, tune up included coolant exchange, but after, temp gauge on dash stopped responding, needle just flopped over to the cold side and lay there. No problems otherwise. Jeep ran great, smoother for the tune up, no problems at start up in spite of bitterly cold winter. Finally in March, brought jeep back to have the coolant temp gauge re-engaged. Auto center replaced coolant temperature sensor, (not sender) after which car would crank but not spark - so no ignition - no start up (impossible to test temp gauge) or drive the vehicle. Had jeep towed to a mechanic's shop. So far we've replaced the Crank Position Sensor - still no spark. Wondering if the replacement of the Coolant Temperature Sensor at auto center may be cause for no-spark.

What do you suggest?

Oxenhandler is offline  
Sponsored Links
post #2 of 3 Old 04-08-2011, 03:44 AM
Registered User
2003 WJ 
Join Date: Mar 2011
Location: akron
Posts: 130
Cts would not cause a no spark condition, however if the crank position sensor is not oem, that could. Does a 95 have a distributor or coil?
wj0313 is offline  
post #3 of 3 Old 04-08-2011, 05:36 AM
It's the crank sensor!
tjwalker's Avatar
1999 XJ Cherokee 
Join Date: Nov 2007
Location: Central Minnesota
Posts: 8,847
I agree, that coolant temp sensor will NOT affect spark.

There are quite a few reasons for a no-spark condition. The #1 suspect is the crankshaft position sensor, which you have already replaced.

Don't replace any more parts until testing verifies the failed part. I hope your mechanic has the knowledge of how to test to the point of failure. If not, find a technician who does.

Start with testing of the ignition coil. They can be tested for primary/secondary resistances very easily.

Other possibilities include a bad ASD relay or a problem with the ignition switch. The ASD relay is located in the power distribution center (black box) under the hood on the passenger side. That relay can be swapped with another relay in the troubleshooting process, as these relays are of the same part number.

Here is the route of how spark is delivered......

Spark: 12 volts from ignition switch to the ASD relay; when the key is first turned on the PCM provides a ground to the ASD relay to energize it, then the ASD relay passes 12 volts to the coil primary side. If no crank sensor signal is generated after a couple of seconds the PCM cuts the ground to the ASD relay (and fuel pump relay too) and that cuts power to the coil (and fuel pump). Key to START and once again the PCM energizes the ASD relay. Now, a critical element is the crank sensor--no signal from the crank sensor and the PCM won't trigger the coil to provide spark

99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
tjwalker is offline  

crank , cts , sender , sensor , spark

Quick Reply

Register Now

In order to be able to post messages on the forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Similar Threads
Thread Thread Starter Jeep Forums Replies Last Post
My First Write Up... Spark Plug Replacement... Curt41 XJ Cherokee Technical Forum 0 01-20-2010 03:26 PM
spark plug replacement steevo025 XJ Cherokee Technical Forum 18 11-30-2007 01:18 PM
Newbie spark plug replacement ??????? 1gopokes1 XJ Cherokee Technical Forum 4 09-25-2006 10:45 PM
spark plug replacement questions spencer411 XJ Cherokee Technical Forum 8 03-06-2006 10:05 PM
Spark plug replacement joemostowy XJ Cherokee Technical Forum 5 03-22-2004 05:15 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome