Changed ignition coil but no crank

lafittejeep

lafittejeep

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2005 Wrangler Unlimited. Started to run rough so pulled over then engine died. I smelled a plastic burn but it was 7pm and no light and got it towed home. Had battery lights radio etc. but engine would not even crank. Next morning popped hood and the center coil was split and white plastic (now hard) oozed out. I never changed the ignition coil before so purchased one and new spark plugs changed everything back together and no crank at all. When I put the key in the start position the gauges didnt even move. The battery shows 12volts but never had it checked yet. Any ideas on why I am getting no crank and no moving on my dash gauges?
 
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Check both battery terminals and cable clamps for oxidation and ensure they are tight on the battery terminals.
When you turn the ignition switch to crank the engine; do you have 12V to the starter solenoid wire from the ignition switch ?
 
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Coiks usually burn up when they cook from being on or having too much voltage. Not sure how the Wrangler PCM makes this function...but on an old school carbureted 60s ish vehicle the coil would get power through a ballast resistor that would cut voltage to 8v ish. The starting circuit would bypass the resistor and power the starter motor so the coil would get 12v on crank.

Usually coils die when they've had too much power...so the theory about short to ground in the PCM sounds valid.

I most certainly would be unwrapping my wiring harness and inspecting everything... especially the spot on the back side of the valve cover where the harness is secured to the stud.

Wiring diagrams and continuity checks would be next...if I didn't find something obvious.

And checking all your fuses...and making sure the correct amperage of fuse is installed...is always a good step!

-Mac
 
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If you have an OBDII reader, see if the PCM is alive and communicating.

If you don't, turn the key on off on off on quickly and the odo will display any codes and then END IIRC.

If you get nothing from those, PCM is not up and running.

For the gauges, hold down the odo reset button then turn key on, then release odo reset button. All lights and gauges in the cluster should cycle on and through needle positions as well as display any cluster failures.
 
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The pcm controls voltage and guages. How ok’d is your battery? If over a year or ever given you issues I recommend changing it as Jeeps are extremely temperamental on voltage.

Did you have any of the topical symptoms of a faulty pcm prior to this? O2 sensors showing bad when good, hard shift from 1st to 2nd when cold, high transmission temperatures?
 
Wranglerfix said:
The pcm controls voltage and guages. How ok’d is your battery? If over a year or ever given you issues I recommend changing it as Jeeps are extremely temperamental on voltage.

Did you have any of the topical symptoms of a faulty pcm prior to this? O2 sensors showing bad when good, hard shift from 1st to 2nd when cold, high transmission temperatures?
Click to expand...
Mark I was wondering if the PCM's driver for the ignition coil rail could have shorted to ground causing the damage to the ignition coil rail which split and melted inside.
 
CharlesHS said:
Check both battery terminals and cable clamps for oxidation and ensure they are tight on the battery terminals.
When you turn the ignition switch to crank the engine; do you have 12V to the starter solenoid wire from the ignition switch ?
Click to expand...
Had battery checked out and it passed so that is next on my check list
 
JKP said:
If you have an OBDII reader, see if the PCM is alive and communicating.

If you don't, turn the key on off on off on quickly and the odo will display any codes and then END IIRC.

If you get nothing from those, PCM is not up and running.

For the gauges, hold down the odo reset button then turn key on, then release odo reset button. All lights and gauges in the cluster should cycle on and through needle positions as well as display any cluster failures.
Click to expand...
I do have a reader but it will not connect to PCM. I will check the gauge reset
 
Wranglerfix said:
The pcm controls voltage and guages. How ok’d is your battery? If over a year or ever given you issues I recommend changing it as Jeeps are extremely temperamental on voltage.

Did you have any of the topical symptoms of a faulty pcm prior to this? O2 sensors showing bad when good, hard shift from 1st to 2nd when cold, high transmission temperatures?
Click to expand...
I have had the battery checked and it passed, I see nothing out of the ordinary on the PCM ( replaced in Oct 2018). No shifting issues prior to incident. Transmission rebuilt OCt 2021
 
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