i've got the motorcraft ignition on a '79 cj w/ an amc 304, i'm getting a really weak spark from the coil, like barely able to see, but i'm gettin 11.5 V to the coil, and the signal side makes a test light flicker, i've checked the resistances and voltages everywhere the chilton's manual and Oldjeep's web page has said to, but nothing, everything is new, icm, pickup coil, coil, ballast resistor, starter solenoid, cap, rotor, everything, does anyone have any idea why i would be gettin a very weak spark, like not even enough to shock u, just enough to feel a light buzz, like less than static electricity does

have you checked the wire from the coil to the distrib and the plug wires?

yes the coil wire only has like 3K ohm of resistance and chilton's says it should have 7700-9000, so i'm guessin thats ok, and i've check all the plug wires, they're good, i've also grounded the coil wire to check for spark and substituted a plug wire on the coil and checked for spark, same results

I'm reaching here...

plugs? (you didn't mention them in the first post)

And just because it's new, doesn't mean it's good... start swapping your old components one at a time

the problem is that i'm gettin a weak spark from the coil, so really no spark to dist. and i've replaced all the old parts w/ brand new, like i just bought them, so i've run out of things to replace, this is actually the second coil i've got, warranty on the 1st one cause thats what i thought it was

not quite what I meant... assuming it worked well earlier

replace your new coil with the one you used to have on there
if same result, put coil back and replace something else
repeat until you've found the guilty component



afterthought: check resistance between block / frame / batt ground.

OK this is giong to sound like a stupid theory, but what did you do and when did you do it to cause the problem you have now?

Did it just magically do this, or did you replace stuff, and then it happened?

Just trying to help you think of why this is happeneing.
A lot of problems are created by humans.
Wrong part...wrong connections, i dunno...think on that theory.

MJ

at this point no theory is stupid, one day i was drivin it around town, parked it and it sat for about 2 weeks, walked out to just start it, just checkin and won't start, so i checked carb 1st, it was good, gettin gas, so then i checked spark, no spark, ok start lookin for things, replaced pick up coil and igintion control module, and it runs for a good 3 days, 4th day go out to start, having touched nothing, no spark again, so pickup coil, starter solenoid, ballast resistor, coil, and all these 1 at a time, still nothing

no other ign. experts, any ideas, anything

kind of off topic aggie, but how did you take off your ballast resistor? the trigger wheel needs to come off, but i cant figure out how to get that thing off there.

Was the Jeep exposed to the elements at any point while it was sitting, or towards the last day it was driveable? Sounds like there is a grounding issue somewhere. Not sure what to recommend other than a shot gun approach, and start checking all grounds relative to the ignition system.

Also, here is some tech info I found in one of my Mallory books for weak spark problems: "Check your grounds especially between the block and heads. If the heads have a weak ground the plugs will not fire very well."

Sounds an awful lot like a bad ICM to me.. any idea of what color you got? (blue/yellow) look on back... Lot of the same symptoms I went through.. replaced distributor, etc.. turns out the ICM was bad. On my Bronco, I carried a spare one.. cause they're not the most reliable.

nomore... just get someone to hold it and use 2 small pry bars and gently pry on it, mine just slid off

the icm is blue, i'll probably be gettin it tested in the next few days and it wasn't exposed to any elements, it's been sittin in the back of the shop, maybe got hot, but not any more than normal

ok, i checked, 0 Ù between battery, frame, body, and motor, and does anyone know what D1, D4, C1 stuff is on the icm, chilton's manual says to connect a multimeter to some of these and i don't know which one is which

Originally posted by big78bronco
Sounds an awful lot like a bad ICM to me.. any idea of what color you got? (blue/yellow) look on back... Lot of the same symptoms I went through.. replaced distributor, etc.. turns out the ICM was bad. On my Bronco, I carried a spare one.. cause they're not the most reliable.
'

the ignition module on my ignition(86 f150) is mounted to the distributer. i didnt think that it had anythig to do with spark out of the coil. i thought it was just for the distributer....

when mine went out i got NO spark what so ever. and it just kind of happened. i hadnt done anything to anything. i would change it out and go from there.