Bad coils?

[rob love]

Pull off a wire at the plug and hold the wire near to the engine....maybe a 1/4" or less. Have someone crank the engine. Is there spark?



Take the cap off the coil to reveal the high voltage terminal of the coil. Pull a plug wire off the engine or use a spare one you have around. Place the wire so it touches the high voltage point as well as near to the block and have someone crank the engine with the ignition on. Is there a spark jump, and is it reasonably strong?


If you do not have a spark, then disconnect the negative terminal of the coil (the wire that heads for the points and condenser), and put a wire from a ground and flash the negative terminal of the coil. When I say flash I mean you literally swipe the terminal quickly. Is there a spark now? If so, then as Chris mentions, it will likely be a condenser. Note there are two condensers involved with that distributor. There is the usual one on the points pate, and there is also a hidden one where the power comes in to the distributor. They can be tested with a meter, and are cheap.



The new coils are a little problematic. One common failure I have seen with them is if you forget to turn the ignition off, the heat of the coil will melt the solder or burn one of the little wires inside the coil.



If you do have decent spark, there are other problems you may have.

You also may have bad fuel, faulty or fouled plugs, or a cracked distributor cap. Try to toss a bit of fuel into the carb opening and see if the truck starts for a second. It may be a stuck needle valve or faulty float.



Simply put, check for spark at the end of a wire first. If you have good spark, then fuel will be your likely problem (or plugs or wires but that is less likely) If you do not have spark, then you have to diagnose your distributor.


A dead engine can also be due to the timing gears. One of them is phonelic,and could theoretically brake. But in having worked with Jeeps for 40 years, I only ever saw that once, back in the mid 80s. The obvious sign of that is that the distributor rotor won't turn as you crank the engine.

[Les Kovacs]

Hi Chris & Rob....its been a while....Rob....you have given me several tutorials on the 67' M38A1 from 2017 to 2019 and that is very much appreciated....I have kept it running mostly through your many detailed responses from axle greases to field timing checks.
Chris...I do remember the many helpfull hints that you have provided during those years as well...thanks.

That said, I do mechanicals...I am not well prepped for electrical diagnoctics...so, if you can both give me your best quess as to what component may have gone bad...I can replace it....Rob....in 2017 you told me start collecting parts big-time as they will get expensive, rare or both...so I did....I have plenty of parts including several military & chinese coils, points/condensors, plugs (8 sets of original plugs), caps etc. So, to review the issue... two weeks ago, I started the jeep for the first time in 7 months....as I "stabill" the engine on storage, it started fast and ran well to the first car show. Two weeks later I started it for the second show----it started quickly, but sounded a little off...about 2 minutes later it started to misfire, hesitate etc until it died. It restarted but died within seconds and it just got worse from there. OK....so at the first car show and the first time in 7 months I fueled up at canadian tire with the no ethanol gas. It took me home but two weeks later the issue occured. Now, I also pulled the plugs after the start but no run issue and they were carbon fouled (not oil fouled)...this is unusual as after 2-3000 miles the electrodes are usually grey to very light tan suggesting good combustion. I have since replaced the plugs with 4 new gapped 2245's and thats it. I was just about to throw in a new coil & points/condensor....but I deceided to contact you guys first.....so, that said, starts & runs one week well and starts but does not run two weeks later....again, the glove box manual trouble shoot guide suggets no fuel or coil issues. So....whats wrong?

It feels great to be back and in good hands.

PS...Shilo is not too bad....I spent 4 years with PPCLI mostly in Shilo an dit was a great experience.

Cheers, les

[Les Kovacs]

Hi Chris & Rob...

This AM I pulled no1 plug wire and no spark through grounded spark plug and no spark through 1/4 " gap high tension lead to ground (engine block).

Any ideas?

Cheers,

les

[rob love]

OK, that's the first step....now we know it's lack of spark and not fuel.
Now undo the 6 screws (or as little as 2) holding the cap onto the distributor and swing it aside. Pull off that #1 wire and hold it from the center of the coil (that little circle) and the other end to the block or some other form of ground. Now (with the ignition on) crank the jeep and you may get sparks from the wire end to ground.
Let us know what you get.

[Les Kovacs]

Hi Rob..not sure what no#1 wire...your distributor picture showing the coil/condensor etc only has wires labeled as A, B etc....I do not see a no#1 wire?

les

[Les Kovacs]

Hi Rob....the picture I was refering too was downloaded several years ago & I assumed it may have been from yours (explaining the distributor system)but regardless....I think I got it after staring at the distributor housing and the 4 plug wires and revewing your email.....so, your last response was to take off the distributor cover, take the #1 plug wire off the distibutor, then take the other end off of spark plug #1. Then take the distributor end of 31 plug wire and have it touch the central part of the coil inbetween the two contacts....then take the spark plug end without the spark plug screwed in and touch the block...then crank and see what happens...is this correct?....if it is....I will try it and report.

Cheers,

les