Coil problems

Bill_F · Post by **Bill_F** » Mon Jun 18, 2012 4:14 pm

Before I spend money on another coil what can cause them to keep going bad. The coil I had in my jeep since I restored it decided to go last week. It was one of the overseas units. I then got a take out original from an m151. It worked for a couple of days but it also seems to be no good now. Any ideas?

capescw · Post by **capescw** » Mon Jun 18, 2012 7:25 pm

Newbie to the mjeep world, but ignition coils in earlier vehicles typically have a dropping resistor (white porcelain) in series with the power lead to limit current, sometimes bypassed while starting. Shorted or defective could cause extreme heating.

Bill_F · Post by **Bill_F** » Mon Jun 18, 2012 8:03 pm

mjeeps do not have those

capescw · Post by **capescw** » Mon Jun 18, 2012 8:15 pm

Original design, true! Unless it's a 12v conversion (or) the original ignition switch was replaced, miswired, and supplies power to the coil ALL the time.

Wesk supplied this diagram, just in case:

http://www.willysmjeeps.com/v2/modules. ... _photo.php

Bill_F · Post by **Bill_F** » Mon Jun 18, 2012 8:18 pm

my jeep is all stock

Post by **wesk** » Mon Jun 18, 2012 11:17 pm

Coils generally fail due to heat.

Heat from an enclosed, un-ventillated distributor such as found on M series jeeps when the vent plumbing is not connected or not connected correctly.

Heat from the power being left on with the engine not running and the points closed.

Heat from a too high charging system voltage, IE higher than 28.5.

Heat from an abnormally hot engine compartment, IE water temps too high, timing advanced to far, or poor air flow.

Imported coils seem to generally have shorter lives.

Used, as removed coils can be very young or very old.

In the case of your M151 used coil it may have been very old.

Bill_F · Post by **Bill_F** » Tue Jun 19, 2012 4:53 am

Everything is hooked and correct. I need to get it running again so I can check the voltage