Magneto Failure?

[LDB C5]

The car is a 26 coupe; 6v. It had been sitting for ~ 20 years. I have had it running and driving several times with no real issues. It "was" running on either battery or magneto. Driving around last week, a bit further than usual, and all at once it started sputtering, backfiring, and finally stalled on magneto. switched to battery, restarted and it ran fine. So far, I have removed and cleaned the magneto contact assembly on top of the hogs head, verified the ignition switch functions, and checked the output voltage at the pin while running on battery. Output is 3 VAC at mid idle speed. I have not pulled the hogs head (waiting on gaskets to put it all back together). Any suggestions? I would prefer not to have to pull the engine f I dont need to.

[John kuehn]

Have you checked the ignition switch? An intermittent cutting out, dieing , and sputtering can all be caused by a simple thing like the ignition switch. Do all the coils fire when the switch is turned on after turning the engine over slowly? Check ALL the ignition and electrical
first before you start tareing the engine apart.
Since you already checked the switch the issue could be further down the electrical circuit.

When you start the car leave it on battery and gently wiggle the key in the switch. Same goes when it’s on mag too. A casual check of the switch sometimes isn’t enough. I’ve been there and done that and later found it had a weak contact in the battery position. Removed the switch and cleaned it up. It was O K then.

[LDB C5]

I have checked the coils (as far as I can check them) and they all function and fire as they should (at least on battery). I have a replacement switch coming on Monday so I will swap that out. I think the magneto voltage may be a little low (3 VAC at a mid idle RPM when running on battery) at the output pin. It runs fine on battery; turn the switch to magneto, and it just dies.

[Adam]

3v is pretty darn low.

Is your magneto pickup post also an outside oil line? Older ones in particular can be a cause of issues and be intermittent.

If your mag got some battery current thru it while running, it could have significantly discharged the magnets.

If your 3rd main bearing cap has excessive end play, it can cause a weak mag. To test the endplay; put the engine in neutral, then in high gear, then pull the front crankshaft pulley forward with a prybar. Did it move? How much? Usually, any amount you can see is way too much.

[speedytinc]

Taking your word that mag contact is clean.
read magneto output without wire connected. check output from idle to hi speed.
confirm that magneto did not accidentally see any dc voltage. wiring & switch all proper.

As your last resort before opening it up or pulling the motor - do an in car magnet recharge. align magnets to field coil, etc.
I have used the 3 or 4 battery method with decent results. 20v-25v mag output, however, using a dc arc welder has got me 35v-40v mag output. (1 spark is all you need).
Metal contamination shorts will correct themselfs.

now retest mag output @ idle & speed. If no change, mag field coil is dead.
Tear down time.

[R.V.Anderson]

Sounds suspiciously like a shorted field coil, usually from a bit of wire such as a broken cotter pin or piece of safety wire. It happens a lot with engines that have sat for a long time and are then put back into service. That happened with my '14's fresh engine; the mag died and tests showed 2V output. The cause was a clutch finger's broken cotter pin inserted by the magnets into the field coil at about the 7:00 position.

[NoelChico]

I had a bad ignition switch in my 26 coupe that would run on magneto, the the next drive was rough running on magneto and the next time died on switching to magneto. The faulty ignition switch dropped juice to the mag and discharged the magnets. I had Ben Martin rebuild it and did an in the car recharge it it runs well on mag.

[LDB C5]

Thanks for the replies, suggestions, ideas etc! I am not aware of and DC voltage being applied to the magneto. Checked the ignition switch, no issues. Replaced the magneto contact pin, same results. I like the following idea "do an in car magnet recharge. align magnets to field coil, etc.
I have used the 3 or 4 battery method with decent results. 20v-25v mag output, however, using a dc arc welder has got me 35v-40v mag output. (1 spark is all you need)." Does anyone have a procedure that I can follow to do this? The only welder I have access to is MIG, so it may be batteries for me. My boat has a 36V trolling motor, so I may be able to use jumper cables and use those batteries.

[jiminbartow]

In 1982, while driving my ‘26 coupe on MAG, I hit a pot hole and the car suddenly died. It started back up on BATT and I drove it home that way. After some trouble shooting, I discovered that the mag post had popped off of the button. The post was dull, so I sharpened it centered it on the button and seated it into the soft solder button. It has run on mag ever since. As someone mentioned, regarding the mag post outside oil line... if the brass fitting is screwed into the side of the hexagonal mag post housing, too far, it can touch the interior mag post contact and short it out. If this happens, back it out some and shim it with washers or grind it off some with a dremel tool. Not only will this cure the short, it will increase the efficiency of your outside oil line by allowing more room for the oil to access the opening up in the mag post housing. Jim Patrick

[Joe Bell]

I would pull the starter and take a look, remove bendix first, then the starter 80% of the time someone has tried to pull the starter with the bendix still on and ruins the field coil, I see it all the time.

[jiminbartow]

Here is the in car magnet recharge procedure I used when I recharged my magnets in 2010. I could not have been more pleased with the results, for 11 years later, my magneto is still running strong and powerful. Don’t take shortcuts like using less voltage or other deviations from the procedure. If you want great results, follow this procedure, for it is a compilation of advice from many of the most experienced and knowledgeable Model T men that frequented the old forum back then, but are now gone. www.mtfca.com/discus/messages/118802/159978.html. Jim Patrick

[LDB C5]

Thanks Jim!! I copied and saved the post that you referenced. I do not have an external oil line, so that's not it. I may have some time this coming weekend. I need to get a compass, and give it a try. I am still trying to understand what could cause the magnets to lose their charge so immediately. The car was running fine and then all of a sudden the issue started. Given the fact that I have nothing to lose, I will try this anyway. Just trying to understand cause. Is there any (simple) way to determine magnet strength?

[speedytinc]

Battery voltage killed your magnet charge. likely ignition switch malfunction.

[Norman Kling]

Before you get to deep in taking things apart, you need to do all you can to try to find and fix your magneto. 3V AC at idle means the magneto is still charging. Just not enough to fire the coils. It might even work at higher speed. To find out, drive about 35 mph on battery, and then put in the clutch to neutral and push the throttle all the way to idle while you are still moving fast. Switch the key to mag while in neutral and then let out the clutch. It might have enough charge to run at higher speeds. Always make a switch to mag with the engine at idle even if the car is moving faster. Because if you do it while in gear you will get a big backfire out the exhaust and possibly blow the muffler!

You can also make this test with the engine running on battery at idle. take the AC ammeter across a resistance from the magneto post to ground. As the engine speeds up the magneto puts out higher voltage. It should go from at least 6 volts at idle to almost 30 volts at high speed. This test is done in neutral with the engine running on battery It might be good to jack up at least one rear wheel and chock the front wheels just in case it slips into gear.

Causes of low magneto output: 1. Magnets need recharging. 2. Magnets too far from coils. This is caused by excessive end play in the crankshaft. Try this with engine not running. Push the clutch pedal all the way into low gear. Then let it back to neutral or high. Go to the front of the engine and gently pry the crankshaft pulley. If the crankshaft moves forward. You have a problem with the thrust surface of the rear main bearing. There are several ways to take out this end play. The best and longest lasting way is to build up the babbit on the rear main cap on the side toward the front of the engine. This will take some work and easiest to do with the engine out of the car. Other ways are to put in a shim on the rear main cap or to attach something at the front of the engine to press against the pulley to keep it forward. I have listed these ways from best which will last longest to easiest which might last only temporarily. On a 26 engine with the 4 dip pan, it is possible to work on the rear main without removing the engine, however, quite hard, and you might need to try the cap on several times to get it right. You will also need to be very careful not to drop anything into the crankcase.

If you do decide to pull the engine, you should go through the entire engine and transmission while it is out and also charge the magnets either off or on the flywheel.

If the engine and transmission are working well now, you could drive on battery until next time you need to pull the engine for some other reason. I ran one on 6 volt battery for about 10 years. It was a little slower on hills but I went on many tours that way. Finally rebuilt the mag when I had the engine out for an overhaul.
Norm

[jiminbartow]

If you do charge the magnets in the car, it is a good idea to park your T facing east or west, so that when the compass points north, you will know that it is pointing toward the N magnet and not toward the earth’s magnetic north. Jim Patrick

[LDB C5]

The car is pointing ENE (mostly E). I picked up some 6ga wire and connectors to make jumpers to reach from the 36vdc battery bank on the boat to the T. I Had no idea how hard it would be to find a compass! I should have one later today. With a little luck, I should attempt this later today or tomorrow morning. I’ll post the results here when finished.

[Dan Hatch]

While I have done this recharging many times, be aware that if you have a weak mag coil you will find out very quick. Dan

[jiminbartow]

When I did mine, the magneto was very weak so it was very difficult to get a reading through the hogshead, so I had to remove it to find the N magnet. That is why it is best to remove the hogshead to visually find the correct magnet position if the magnets are totally dead. Jim Patrick

[Chris Barker]

If you remove the hogshead access cover, you can see the ends of the brass magnet screws and use these to get the flywheel exactly aligned. Three 12v batteries does it, but I suggest that the connection you 'touch' to charge it is against the hogshead. Connect the top terminal properly. I fix a tiny ring spanner onto the terminal and then clip the jump lead to that.

[speedytinc]

You can determine magnet position by pulling top inspection cover. No need to remove hogshead. Once you are in the ballpark with your compass align brass magnet screws evenly to mag post connection. (part of recharging instruction).

[Adam]

You can determine magnet position by pulling top inspection cover. No need to remove hogshead. Once you are in the ballpark with your compass align brass magnet screws evenly to mag post connection. (part of recharging instruction).

Are you sure about that?

[speedytinc]

Absolutely. you got to get your head down really low or use a mirror.

[Norman Kling]

I think what Chris says he uses on the terminal, a "ring spanner" is what we in United States call a box wrench. Just in case someone might be puzzled.
Norm

[Chris Barker]

No; not a box wrench, if that's a hexagonal ended tube. Just a small wrench that's a ring, not open-ended. Maybe 1/4AF or 5/16AF so it goes under the terminal nut.

[LDB C5]

I tried the compass, and cant seem to get the needle to point directly parallel with the engine. I will remove the inspection cover and try to align the contact screw with the contacter assembly pin manually. I have "crimp on" ring connectors for the cable so that I can attache it to the contact pin. My plan is to "flash" the circuit to either the hogs head or the frame.

Question: Should the brass screw make direct contact with the pin?

[speedytinc]

If you can get the compass to be generally north. (or south depending on which side you are lining up on)
Look at the magnet screw ends on the flywheel. rotate the flywheel enough to center those screws equally to both sides of center mag post. Double check for your north reading. You are ready for the ZAP.

I am not real keen on running voltage thru the mag post connection. I prefer to remove it & make the connection directly to the field coil solder blob.
I use an old valve with a piece of tubing to insulate to make the contact. hold it down tight. (dont want any accidental arcing in this area)
This is manditory when using an arc welder for the recharge.

[speedytinc]

sorry, i dont understand your question about a screw & pin.

[LDB C5]

your post 7 posts above this one. I am guessing I need to split the screws evenly with the contact post in the center. Also; i have the old contact assembly that I can use to "flash" the magnets, then replace it with the new one when I am through. From what I have read; 3 or 4 arcs should suffice per magnet. Just to clarify: + to the contact pin when N is aligned; - to contact pin when S is aligned; Correct?

[speedytinc]

Follow the written or pictorial for proper polarity to match compass check location.
No need to do each magnet pair. A good field coil has 14 electromagnets to charge all the magnets at the same time.
leave the flywheel in its correct location for all 3 or 4 quick strikes.
Mag post connection is solid. strike spark on hogs head.
When done, leave magneto contact wire off . Check output @ idle thru fast motor speed.
If sucessful you should read 10+ volts @ idle & 30v+ @ hi speed.
If no change, & your charge was hot enough, (not sure that a 16 gauge wire will move enough amps) field coil may be fubar.
if successful, hook up mag post wire. If , or when you loose that magneto voltage, you still have a voltage leak going back thru to magneto.

[speedytinc]

I look up polarity every time. I dont trust my memory for this kind of stuff.
For fun, after the recharge, before you move the flywheel, check your compass, you should see a much stronger needle propensity.

[LDB C5]

Not 16ga; 6ga.

[speedytinc]

that should be fine.

[SurfCityGene]

Here's another very respected opinion from a multiple time winner of the Montana 500, Tom Carnegie.

http://www.mtfca.com/discus/messages/50 ... 1431523227

He uses a very simple method to recharge the mag in the car with no E /W pointing or Compass thing. He also has some good safety tip[s about where to apply the voltage when doing in the car!

Please check it out and you'll see it's a much simpler and proven way to recharge your magnets.

[LDB C5]

SUCCESS!!! Three flashes (36 VDC). 20VAC to ground at the pin! Runs on magneto again! I’ll swap the ignition switch and hope for the best.

A very sincere THANK YOU to all who helped the neophyte through this issue!

[speedytinc]

congrats!!

Gene: there is the opinion that if charged backwards, magnets can revert to there original polarity. Didnt want to buck the experts.

Our good friends arc welder power source recharge has showed me the way to go. That method produces the exceptional recharges. (40v)
As good as individual magnet charges.
His experience i respect.
We have both seen the amazing results on a weak magneto in car charge.
Next time i do an out of car rebuild/recharge, i am going to lay a field coil on the magnets for the charge with the arc welder. That saves a lot of labor costs over individual magnet charging.

I have used the battery method with good results, but not exceptional results.

[RajoRacer]

Individual magnet charging is the ONLY way to determine if a magnet is cracked ! If it won't hold a charge for 24 hours, it's most likely cracked. I only recharge magnets in the same polarity I find them on the flywheel.

[SurfCityGene]

Steve, Don't know if you followed that post several months or a couple of years ago when Tom C. did several tests and researched about the polarity reversing issue of a magnet. I always thought you had to keep it the same but according to Tom's extensive studies and testing he found that it was not necessary.

I know lots of folks will not agree but it is worth looking at. Thanks for telling us about the cracked magnets!!

I just think it's so sad when we read about guys tearing apart a running engine or converting to a disy just because it quit running on mag when it's so easy to first try giving them a recharge with only removing the trany cover.