Originally Posted by jrsjeep
I have searched this topic and seen a lot of responses but unfortunately none that have been specific to my combination.
I am running an 85 CJ7 with the 258, freshly rebuilt, bumper to bumper painless wiring harness, duraspark ignition and TBI conversion.
The Jeep runs great for about 20 minutes then begins to misfire upon acceleration. my first coil burned up on a camping trip, it was literally smoking. I bought a performance coil from autozone to get me home. and it is working, 20 minutes at a time. it only has to sit for 3 minutes at a time to be cool enough to run again.
again, I didn't see anything exactly pertaining to this situation, but I have checked my grounds, I have added a ballast resistor, it has not made a difference. with the rebuild, the duraspark module was replaced. I was looking at MSD ignition coils today, but I think what I have should work. if I do go the MSD route, can I just get a coil or do I need to get the control box also?
thank you for the help you gave me during the build and for any now.
Painless harness... NO RESISTOR!
If you have the 'Factory' ignition module, you need AT LEAST a 1.35 Ohm resistor to keep the coil/module alive...
The only SURE way to kill a coil is bad ground to the ignition module.
Since the coil 'Grounds' through the module, then the distributor in your year model...
The 'Ground' for the module is at the distributor to engine block connection.
If the engine isn't getting a good 'Ground', then the ignition isnt' getting a good 'Ground'.
That's why I recommend a DEDICATED 'Ground' to the module 4 wire connector 'Black' wire, harness side.
With this dedicated 'Ground', the module/coil ALWAYS has a direct 'Ground' path to complete it's circuit.
Resistance doesn't shoot to the moon, and your coil stays alive longer, along with the ignition working MUCH more efficiently.
As we have discussed here several times, most of the CJ 'Electrical Phantoms' go away with dedicated 'Grounds'.
Again, the CASE OF THE MODULE OR THE CASE OF THE IGNITION COIL DO NOT 'GROUND' THE SYSTEM...
Trying to add ground wires to them is a waste of time and money.
The system 'Grounds' though the 'Black' wire at the module 4 wire plug... (Which goes to the distributor/engine block)
How do you have the module wired with that 'Painless' harness since ignition harness isn't supplied?
If you powered up the 'White' wire to the module, I'm surprised the vehicle runs.
If you powered up BOTH 'White' and 'Red' wire to the module, the module is the next thing to die.
The 'Proper' way to keep both module and coil alive is to have the 'White' wire powered when cranking the engine, via the 'I' terminal' on the starter relay.
When the key switch turns back to 'Run', the 'RED' wire to the module should be what activates the module.
If both are active, or just the 'White' wire is active when the key switch is in the 'Run' position, you will have problems with both module and coil.