No Fire - Crazy Ignition

Well I got another Jeep, this one's a '74 for cruising the feild outback, but I can't get the thing out of the driveway!! I get no spark and no juice to the high voltage coil to distributor wire. I put in a new pick up assmb in the dist, but no go. I pulled a coil out of another running Jeep, but still no go . The coil has power to BOTH low voltage leads with the ign switch on. The wire leading out of the dist splits into two wires and then vanishes into the wiring harness, re emerging from the harness is a green single lead to the - side of coil and two red wires to + side of coil.
Any Idea??

 

The coil you pulled from another running jeep, was it a similar motor/distributor/ignition system? I'm thinking out loud here... and am relatively unfamiliar with the '74 unfortunately, as my '75 has an electronic ignition. If you have power to the 2 inputs, it doesn't make sense that you wouldn't have it to the distributor. Have you replaced the wires?

What motor is in yer '74?

By the way, congrats on the new jeep (that's the third, aint it?).

 

The usual problem with the stock Prestolite electronic ignition is a bad module (rectangular block on the inner fender). The only other electronic part is the reluctor coil (aka pickup coil). These systems are very sensitive to corrosion in the connector between the distributor and the module.

 

Hey Plunk!
Actually this is currently the seventh Jeep I now own. And three of them run! The newest Jeep is the first year for the electronic ign (serial no. says '74, titled as a '75). It does have the pick up coil inside the distr. - and I just put in a new pick up coil - the engine is an inline 6 (not sure if it's a 232 or 258) - I took the coil out of my '79 with the 258. What stumps me is the positive charge to both sides of the coil at all times - even when I crank it over. I thought one side of the coil should have juice, but the other side should only have a positive charge for a split second, and that was what triggers the coil to fire the high tension lead to the distributor.
thanks

 

Ballast Resistor?

 

IIRC no ballast resistor with the Prestolite system. Ballast resistor is only required to drop the voltage enough to keep from burning the points. No points -> no ballast resistor.

 

The module opens/closes the circuit to the coil, just like points. If there's no module, the coil circuit will be floating and both sides of the coil will be at +12V. Same thing can happen with a bad module.

This is the module, not the pickup coil. It's about the size of 1/2lb of butter and located on the inside fender.

 

Tim,
The guy I bought the Jeep from said he just put a new module on, and indeed it looks new , but it is larger, (perhaps the size of two sticks of buter side by side!) and gold colored. Any good way to check if I screwed up putting in the pick up coil or the p.o. put in the wrong/defective module?
Thanks,
Bob

 

Hi Bob - there may be a test for the module... if I were home, I'd look in the TSM. Any TSM from '74 to '77 ('78?) should cover the Prestolite ignition. Yes, the module is about the size of 2 sticks of butter. My truck has a Napa module and it's gold-colored.

Most of the time, you replace the module when you've eliminated all other problems. If the 12V and ground signals are correct at all points in the circuit, the pickup coil has continuity and is positioned correctly wrt the trigger wheel, the coil is good, etc. then it must be the module. If you want, you can sub a points-style distributor from a '73 or older AMC I6. There are also plenty of articles on the web about replacing the Prestolite distributor with a HEI distributor from a GM I6 (usually a 250 from around 1980).

 

Bob, I have a service manual for the '75 and I have an extra electronic ignition module... Let me know if there is something specific I can look up for you. Or, you could use the extra ignition module to determine if that is the source of the problem.

 

I finally figured it out, the previous owner put the module in and plugged in the plug wire, but there was this last black wire with a plug on it - the ground! I grounded that wire and got spark! It still won't run, but now I have spark.

 

Live and learn. Gotta learn them lessons the hard way sometimes... we all do it.

What seems to be the problem now?

 

Not sure what's wrong now. I have spark, but it would not start, not even really sputter, but acts like it wants to, so I've been playing with the distributor, seeing if it was out of whack, but it's tough to do by yourself - turn the dist a little and then run around and crank the ign - got to get me one of those remote starters! Ether doesn't do any thing. The fuel pump puts a healthy spurt of fuel, which leaves me with the dreaded carb problem. I have an old Carter from my '79 (put on a Weber - great move!), but the mounting flange is different. Will try to play with it Thurs.

 

Couple things... if you want a hand, I can stop by and give you some help. Send me a PM if interested.

Try removing each spark plug and squirt a bit of oil in each cylinder (not a lot, just a couple squirts) and turn the motor over by hand a few times. I had the problem that all my trying (gas and starting fluid) had washed the cylinder walls clean and I had no compression at all. The oil trick was all I needed. Only smoked for about 10 seconds once it fired. Give it a shot.

 

finally got one of my boys to crank the key while i moved the distr, and it ran!! only for about two minutes, but it lives! Ran out of daylight tonight , but tomorrow's another - if only I could figure out how to get of camping with the family this weekend, I could really get her running (maybe).

 

Good luck Bob.

 

Still no luck keeping this thing running. I just bought a large capped HEI distributor/coil on Ebay. Apparently you can swap these into the Jeeps with a dist gear change, will let you know how it turns out.