I'm trying to figure out the issue with my magneto and I'm stumped, so to the experts I go.
Here's the facts:
1. Car ran fine on bat and mag when we pulled it out of storage in Nebraska. Drove it about five miles on country roads.
2. Transport it to California, car starts and runs on bat and mag fine. Drove it around the neighborhood, all is good.
3. Replace coil box with the one that holds newer coils. Coil box in the car was made for Kingston coils. Coils were jimmy rigged to work, but they did.
4. Replaced points on coils (K&W) and adjusted with ECCT. All four coils adjusted fine except for capacitor test. Coils were bought new in 1953 by my grandfather.
5. Replaced timer, timer wiring, spark plug wires, mag wire to coil box with new.
6. Rebuilt carburetor.
7. Replaced magneto post with a new one from Fun Projects.
Fast forward to today:
Car starts easily on bat but when switched to mag dies.
A. ECCT test shows weak mag.
B. 1156 bulb test shows 8v AC on my analog voltmeter when running on bat.
C. No load voltage on mag at idle is 12/13v ac.
D. Verified coil box switch connections are good and not shorted.
E. Switched the wires around from bat to mag and same issue. Car will start on bat but die on mag.
F. Replaced mag post to coil box wire and same issue.
G. With my VOM on lowest ohm settings I get 2 ohms from mag post terminal to ground. Same if I go from the coil box switch mag contact to ground.
My conclusion is:
1. Coils improperly adjusted.
2. Magneto has issues.
I don't understand why it doesn't run on mag when it did prior to my replacing the parts above.
you mentioned that capacitor test on coils was not good. They must have good capacitors to work properly. When you replaced the various parts, did you replace one part and then try to drive the car, or did you do all the work and then try to start?
If it were mine, I would borrow a set of coils known to be good and substitute them. See if that fixes the problem.
I don't think you have a carburetor or timer problem or it wouldn't run on battery. So this leaves two things to my mind which could cause the problem. The wiring between the mag and the coil box, the switch or the coils themselves. Since you switched the battery and magneto wires and had the same result, I would suspect, perhaps the ends on the wire are not making good contact. Try either a different wire or solder the connectors to the wire and see if that fixes the problem.
Take off the magneto terminal and see it there is any "fuzz" or any other type of debris on the "pointy end" on the bottom.
Is the magneto terminal an original type or an outside oiler type?
You need to adjust the coils properly using either a hand cranked coil tester or a Strobe O Spark.
New mag post installed, verified that magneto button visually looks good with mirror, felt it with my pinky finger and it felt solid.
Mag terminal is an original style from Fun Projects, excellent product by the way.
Agree with Royce to exchange coils with another set to eliminate them as a problem source.
Tomorrow I plan to double check all the wiring to confirm I didn't do something stupid.
Thanks to all
One important thing to know if the car still has its original round field coils. There is a narrow setting of the spark lever for each setting of the spark lever where the car runs perfectly on MAG. One notch above or below can make a difference.
You still need properly adjusted coils. From what you say the magneto output is adequate.
Today I had a chance to do some more diagnostic work. Sunday I replaced all four capacitors and set the coils again with my ECCT. All four are now properly tuned.
Car started on battery ok but didn't seem to run that good and then I did the screwdriver to ground test and found #3 cyl dead. Took a look at the coil and it was not firing. Checked everything again and didn't any wiring or timer issues. So I swapped coils and re-shimmed them and #3 came to life.
It looks like I need to make slightly thicker shims to push the coils against the contacts.
Car now runs on mag and battery.