2001 Grand Cherokee ignition coil failure

Reply

  #1  
Old 04-16-10, 07:35 AM
Member
Thread Starter
Join Date: Apr 2008
Location: Mexico
Posts: 34
2001 Grand Cherokee ignition coil failure

I would know, how can I test the ignition coil pack? and the voltages of the connector to be sure if I need buy another one, or know if the fail is in the wiring or other device.
2001 Grand Cherokee 6 Cyl. 4.0L
Thank you.
 
Sponsored Links
  #2  
Old 04-16-10, 05:36 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Does it trigger the check engine light? What is it doing? Is it misfiring? At what speed range(s)? Worse when damp out? Can you see any sparks jumping along plastic cover out under the hood at night? Is the cover clean of any greasy dirt?

For actual testing - I am not sure there is a surefire test with the vehicle say turned off(unless of course if the coil were completely dead). Testing with an oscilloscope hooked up with engine running and possibly put under a load would maybe show something.

Also, if that is where the suspicion lies, you could weigh out cost from junk yard to that of pro-analysis, and likely pro-replacement (as one might be too embarrassed to have it tested, say confirmed, then say you will DIY it at home?).
 

Last edited by ecman51; 04-16-10 at 05:40 PM. Reason: added more
  #3  
Old 04-16-10, 07:40 PM
Unclediezel's Avatar
Member
Join Date: Dec 2006
Location: Northeastern PA.
Posts: 2,230
Coil packs on Jeeps VERY RARELY fail entirely.....The most common problem is the plug boots rott and the spark leaks out to the head. That would cause a misfire in a cylinder or two, but not an entire pack.

Chrysler uses a Main power relay....(A.S.D.- Auto Shutdown) to supply fuel pump , Ignition coil, Fuel Injectors, and possibly O2 sensor heaters with power.

Does the truck Run????----What lead you to suspect the Coil??? Is there adequate fuel pressure????( The test port is on the center of the fuel rail, on the drivers side).

While Junkyard parts do make great test pieces....Without a definite direction to follow, even used parts can get expensive . Throwing parts at it may turn out to be more of a burden than just breaking out and having it fixed.
 
  #4  
Old 04-17-10, 08:28 AM
Member
Join Date: Oct 2008
Posts: 1,312
On spark testing tools... it appears that these tools, which look similar to spark plugs have a large gap of .25 inch.

So I guess they have a much larger gap than a spark plug and that is the test. That if there is enough voltage to make a good spark with this testing tool, then your coil is working ok.

A properly working electronic ignition system will be able to jump a spark across a spark tester's spark gap (preset at .25"). You should see a crisp blue spark.

Here is the tool...
Kent-Moore J-26792 HEI Test A/C Plug

Here are more spark testers...
Spark Plug Testers & Spark Plug Ignition Testers | Toolfetch

Another thing to check for is cracks in the spark plug wires. If you see cracks, replace the wires. Or look at the engine running at night. See if there are any sparks on the wires.

An interesting fact: Higher cylinder pressures and/or more fuel (more rich) will need a higher voltage for there to be a spark.
 
  #5  
Old 04-17-10, 04:42 PM
Unclediezel's Avatar
Member
Join Date: Dec 2006
Location: Northeastern PA.
Posts: 2,230
Originally Posted by Bill190 View Post
An interesting fact: Higher cylinder pressures and/or more fuel (more rich) will need a higher voltage for there to be a spark.
I remember when I was young in the business, Watching guys standing at an oscilloscope, talking about Low compression and firing voltages. I know now that it makes a difference, but after all of these years, I still have no clue as to why....

A 4.0 L jeep has no plug wires....It has one long "Pack" which spans the length of the engine, With 6 little "Booties" that fit over each of the plugs. I suppose you could unbolt it , flip it over and test under "Cranking" conditions, ..........<<<<<OOPS>>>>>> Mother Mopar strikes again...the Harness is too short to lift the pack up, and there certainly isnt enough slack to flip it. If you remove it completely, you could probably "OHM-Test" it......The green/black wire in the connector is common power....So you would read from common to each of the triggers. "reasonable guess at best.
An open coil will indeed set a check engine light....but the truck would need to be running before the PCM self tests would occur.

This is basically a simple "No-Start" diagnosis, which with basic preliminary knowledge and basic electrical tools (A 12v Circuit tester , I consider basic..) Should prove "Do-able" without Guesswork or "PArts Tossing"
 
  #6  
Old 04-17-10, 05:07 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Originally Posted by Unclediezel View Post
I remember when I was young in the business, Watching guys standing at an oscilloscope, talking about Low compression and firing voltages. I know now that it makes a difference, but after all of these years, I still have no clue as to why....
I guess then we can consider ourselves lucky that high compression diesels then found another way to fire.
 
Reply


Thread Tools
Search this Thread
Display Modes
Posting Rules
You may not post new threads
You may not 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 On
Pingbacks are On
Refbacks are On



All times are GMT -7. The time now is 11:03 AM.