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Weak spark and I'm searching for the cause
Posted to Technical Discussion Forum on 1/25/2016 20 Replies

I am working on a Jeep Liberty 2.4L. You can see the TechHelp that I started here:

The spark coming from the ignition coil is very weak. It has a yellow/orange color instead of a bright blue, normal hue. All four terminals are sparking and look the same. I have tested all of the coil wiring to the PCM and all checked out. I scoped the CKP, CMP, TPS and traced all of the associated wiring of each and they are good. I have 12v coming from the ASD relay and both of the signal wires flash brightly using a test light. Today while following the diag tree, I changed out the coil with a known good OEM unit with no change whatsoever. What could be the cause of the weak spark? What controls the spark output? Possible grounding issue? Here is the kicker, sometimes the truck will start and run like normal. I have not been able to check what the spark looks like when this happens but I can only assume that it is normal. When it is acting up, it has an extended cranking issue. It will crank and crank then finally start, probably due to the super weak spark signal. Thank you for any input. I am about to give up on this one, its consuming me.

Shawn Freeman
Country Road Tire and Auto Service
Kittanning, Pennsylvania, USA

20 Replies Received (View Replies)


car Vehicle Data

2003 Jeep Liberty Sport 2.4L

Engine2.4 L
Trans5-speed Standard