Coil failure?

Howdy y'all,

Havn't been able to get my 71 Jeep CJ5 w/ a 225 V6 started for the last few weeks. Looks like the coil is the culprit. It's supposed to read 1.13-1.23 ohms across, but I'm getting 2.2-2.5. Also not getting any power across the leads when I crank the engine. The fuse is fine, checked that. Could there be a short somewhere in the primary circuit? I'd think that even if the coil was bad, I'd get a voltage reading across it while cranking.

 

Remove wire from neg side of coil. Turn key on. check voltage agn at pos side of coil. If no volt then check at both sides of ballast resistor. That will give answer.

 

1 or 2 ohms is a ridiculously low resistance so reading a voltage across it might be tough.

I wouldn't say right away that the coil is bad just from the resistance. 1 ohm of resistance could easily be just a bit of corrosion or dirt on the contacts. Like I said, 1 ohm of resistance is REALLY low.

I had an ignition problem last year and just gutted the whole system. Honestly, I came out under $70 I think for a new coil, plugs, distributor cap, rotor, points and condenser. I had a bit of trouble with the points. Apparently the ones I got had too weak of a spring but besides that it was pretty cheap and easy to redo. If you're going nuts trying to find it it may just be worth doing the whole system.

 

Yes, it's very hard to measure low resistances reliably.

Every Jeeper should have a spare coil (hint). If you have a coil failure back in the woods, you're stranded until you get a new coil or a tow can reach you. BTDT.

The position of the points will determine whether the coil terminals show 12V or 0. With the points closed, almost all of the voltage drop will be across the ballast resistor, which is upstream from the coil, and voltage drop across the coil will be minimal. With the points open, you should measure 12V (battery voltage) on both terminals of the coil.

 

Unfortunately I havn't been able to get anyone to help me crank the engine over the last few days so still waiting to test all your methods. Thanks to everyone for their replies.

 

I don't think you'd get 12v at the coil after the current passes through the ballast resistor.

 

Tim said (with points open) at which there is no circuit to ground therefore no current drop there and voltage will be same as battery.

 

Now I'm a bit confused on what I should see at the coil. I'm not getting any power across the coil no matter whether it is cranking or sitting still.

Should the coil read 12V when the points are not in contact (open) and the ignition is turned on, but not cranking?

Does it matter that my front lights and heater are disconnected? I don't think it would judging by the wiring diagram.

 

Grrrr.... finally got to do some testing. Here's the update.

Coil passes all resistance tests.
The drop across the ballast resistor is within specs.

I do not get a voltage reading across the coil's terminals. I'm pretty clueless at this point so guess I'll be picking up a new coil and dist cap tommorrow.... dammit

 

You say your not reading voltage across coil terminals? You need meter pos lead to either coil terminal with points (OPEN) AND the meter neg lead to ground before you will read any voltage if there is any there.

 

I put an hei in mine and have all the old stuff, coil, wires, distr, even the good plugs you can have it if you pay for shipping (or any part of this stuff) I dont guess a new coil costs much but keep me in mind. it all worked great, just getting modern

 

Shouldn't there have been a voltage across the coil terminals while cranking? Even if it would have been sporadic?

 

Would to small of a gap (0.28") cause there not to be a visible spark?

 

w3srl: With the ignition key on, I do get 12V on the hot side & 9.6V on the 'downstream' side. The voltage drops a little while cranking. I'll try to run a jumper wire from the coil to the battery & see what happens this morning. Thanks to everyone for the help. I know we've all been in the position where it's 'NOW WHY THE HELL ARE THEY BLINKING?' [You get a gold star if you can figure out where that's from]

Orangeaid: I'll def. keep that in mind. I was looking at the HEI upgrade last night a bit, worth it?

 

I put an HEI on m 68 oddfire and it works great. I think well worth it.
I got it from these guys in your part of the country.
www.crtperformance.com

 

Solution found:
I went and rechecked all the voltages and resistance starting from the beginning to end. Originally I was getting 12V & 9V on each side of the ballast with the rotor closed. Tried it again, and got 12V & 0V with the rotor closed. I jumpered over the ballast resistor and wallah... the Jeep started. I don't understand it but I'll be getting a new ballast resistor soon I guess. With the jumper though, it wouldn't idle on it's own.... I really hope replacing the ballast resistor will do the trick.... thanks for all the help y'all

 

Well, I hope that's your issue. New resistors are cheap.