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2001 Jeep Wrangler 4.0 TJ coil rail

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3 years 9 months ago #42308 by Wiggs
2001 Jeep Wrangler 4.0 TJ coil rail was created by Wiggs
I'm testing the coil rail using bi-directional controls on a scan tool. When I manually fire a certain cylinder the other cylinders are also Illuminating the light I am using. Are all the coils firing at once? this is a waste spark system

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3 years 9 months ago #42309 by Donut
Replied by Donut on topic 2001 Jeep Wrangler 4.0 TJ coil rail
It's probably feedback from the firing of the one coil. All 3 coils have a common 12v power feed and when one coil fires you'll have an inductive kick along the primary wires and depending on what kind of light you're using it may be enough to light it.
"Don't ever say 'easy' until the check clears."

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3 years 9 months ago - 3 years 9 months ago #42311 by Noah
Replied by Noah on topic 2001 Jeep Wrangler 4.0 TJ coil rail
It is a waste spark system.

4 wires, so one common feed and 3 coil drivers.

The bidirectional test with the scan tool may fire them all at once, but that's not the way it works with the engine running.
"Ground cannot be checked with a 10mm socket"
Last edit: 3 years 9 months ago by Noah.

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