Suddenly stops running on magneto, What do i look at next?

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Model T Ford Forum: Forum 2012: Suddenly stops running on magneto, What do i look at next?
Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Sunday, June 17, 2012 - 12:05 am:

So i was driving home and i thought i ran out of gas, Backfiring with no power. When i stopped i saw i still had fuel so i turned the key to battery and it ran fine so i started driving and when i switched to magneto the engine would barely fire, Backfire alot and die. Checked the wire on the post, It was frayed and shorting out on the firewall so i put some tape over it. Still didn't help. Cleaned the mag'post it had no lint. Cleaned the key contacts with still no improvement. Put my 6-24volt test light on the mag post, It lights up and gets brighter as the speed increases and when the key is turned to mag' it goes slightly dimmer.
Doubt the coils all had their capacitors die at the same time so is it possible the magnets fell off without me noticing? Can a magneto fry itself through a short circuit? Doubt it as it looks tough. And no i do not have magneto lights or anything that might be influencing it. What would cause this? How do i fix it?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Thode Chehalis Washington on Sunday, June 17, 2012 - 12:31 am:

Kep,
Probably the first order of business is to check the voltage with an analog meter.

Read this thread:
http://www.mtfca.com/discus/messages/257047/282864.html?1334956032

Including this link:
http://coildoctor.com/yahoo_site_admin/assets/docs/MAGNETO_TEST.58163152.pdf

Once you do that you should have a better idea where to look.
Jim


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bede Cordes, New Zealand on Sunday, June 17, 2012 - 02:03 am:

Kep,

looking at your posting on another thread, perhaps one of our country's ethnic people has sabotaged your magneto.

As Jim has suggested, do the lamp test on the magneto terminal output post with an ANALOG voltmeter with the wire disconnected and running on battery, and work from there. You'll either end up working "in", into the engine innards, or "out", into the cars wiring, switch etc, to trace the fault. I hope you end up working "out".

Good luck !

Bede


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, June 17, 2012 - 09:46 am:

If the wire was frayed and shorting out you probably have similar problems inside the coil box. Measure voltage at the mag post, then if it is good you know you simply have a bad connection somewhere between the mag post and the coils.

The ignition switch often causes these sort of problems.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Bishop, San Diego on Sunday, June 17, 2012 - 03:04 pm:

kep,
Same thing happened to me a couple of months ago. Turned out I had a short in the ignition switch, and a short in the coil box. Caused the magnets to demagnetize in the magneto, and then it runs as you describe. Even if you tape up the frazzled wire, the short has already demagnetized the magnets.
Read the suggestions above for checking mag output and continuity (very easy with ANALOG voltmeter).
I rewired my ignition switch and coil box (much easier than I expected),altho it sounds like you need to rewire or replace the wire to your mag post. Then did an in-car recharge of the magnets (also very easy, 20 minute procedure). Now runs great on mag, actually better than before! 30+ V output at speed.
If you need diagrams for in-car recharge, let me know. Good luck.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Sunday, June 17, 2012 - 07:06 pm:

#1. Check the voltage with an analog AC voltmeter parallel to a light bulb. Should approach 30 V. AC at high rpm and at least 6 volts at idle. If voltage is low, the problem is in the magneto. If voltage is OK the problem is beyond the magneto. Could be wiring, switch coil box. timer, or coils. A quick check here would be to borrow a set of coils which work well in another car, and see if it makes a difference in your car. If it does, you might need to rebuild your coils. If it makes no difference, check the wiring, the coil box and the timer. Note sometimes the timer will make a difference where you set the spark lever, especially if the timer is dirty. Try moving the spark lever up and down and see if it has a "sweet" spot. If it has a spot where it runs better than others, you might need to clean or replace the timer.

Good luck,
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Patrick on Sunday, June 17, 2012 - 07:14 pm:

Mine did that after going over a pothole. Turned out the magneto post point slipped off of the magneto contact solder button. Remove the mag post, inspect and if dull, possibly sharpen and straighten the contact point and screw it back in so that it makes contact with and embeds into the button of solder. Jim Patrick


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Hatch on Monday, June 18, 2012 - 08:52 am:

One of mine did that and I hope yours is not the same problem I have. One of the flat plates that hold the magnets on came off and ate the mag coil. :-( Dan


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Friday, June 22, 2012 - 01:37 am:

Plate plate coming off sounds about right. Not sure why people believe in analog volt meters, Never seen one in 10 years now.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bede Cordes, New Zealand on Friday, June 22, 2012 - 02:08 am:

Come on Kep,

it's been written numerous times on here why you should use an analog meter for testing the magneto output. :-)

In simple terms, Model T coils can emit "nasty" electricity that can cause inaccuracies and problems with a digital multimeter. An analog meter is pretty simple electrically and internally, and doesn't get bothered by this "nasty" power. Hence, it is the recommended instrument to use.

To put it into Kiwi terms, it's a bit like plugging in your latest electronic toaster right next to an electric fence unit that has a bad earth. The high voltage from the fence unit would probably eventually stuff it, but an old toaster from 30 years ago that has no electronics and a simple bi-metal timing device, will just shrug it's shoulders and keep on working.

I'll agree Analog multimeters are getting harder to come by (new) for Joe Bloggs, but they are obtainable on Trademe, or any electrical wholesaler (ie Ideal, Corys, Powerbase etc) can obtain many types. Forget about Dick Smith or similar, they would not know one end of the dial from the other.

Good luck,
Bede


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Friday, June 22, 2012 - 03:11 am:

Dick Smith no longer even sells diodes! i know i will need that good luck.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas Mullin on Friday, June 22, 2012 - 09:20 am:

Kep,

The other advantage of the analog meter is the D'Arsonval Movement is continuous reading. As your voltage or current fluctuates the meter will follow. Being a physical device, it will also damp the fluctuations a bit giving steadier readings. A digital meter takes a sample over a short period of time and you are likely to see the numbers constantly changing. Same readings as the other meter, just harder to find the "true" reading.

Radio Shack here in the states still sells them. Since they are light weight, shipping to NZ shouldn't cost too much.

radio shack


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Friday, June 22, 2012 - 10:35 am:

If you're really lucky and Junior's boss decides to get rid of some old stuff you might end up with this. He saved it for me after I told him about T's and digital meters.(a little photo flash on the meter face).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Friday, June 22, 2012 - 11:03 am:

Your problem doesn't sound like mine, but it could be a variation of it. If so, you need an outside oiler. The magnets hit the funnel on the inside oiler which broke it off and cut the copper which instantly made the magneto go dead. I didn't find out what had happened for 10 years. Fortunately I had an outside oiler and between what was left of the inside oiler and the outside oiler the bearings were not damaged after driving 10 years on battery. It is possible that somewhere inside, the magneto is grounded to the ring other than the ground at the end of the ring, which would give you only the coils between the ground and the magneto post. Or it could be that the crankshaft endplay is too great, causing the magnets to be too far from the coils, or the magnets are weak. You will not know unless you do the voltage test with the analog voltmeter. Then if the voltage is OK you can look elsewhere for the problem. If the voltage is low, then you will need to check for endplay or try to recharge magnets in the car, before you pull the engine to fix the magneto.
Good luck,
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Aldrich Orting Wa on Friday, June 22, 2012 - 11:37 am:

Simpson 260. I fixed many an airplane with one of those!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Friday, June 22, 2012 - 11:43 am:

John: are the correct leads for it available any where?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Kekacs on Friday, June 22, 2012 - 12:57 pm:

Ahh I love the Simpson I learned how to fix computers with that puppy.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Friday, June 22, 2012 - 01:49 pm:

Dozens on e-bay. Simpson still sells it too. But re-conditioned and quite pricey there. Sells lead sets for $30.00+. Note the "home mades" in the pic.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep NZ on Friday, June 22, 2012 - 03:35 pm:

Free shipping on orders over $50? Might have to get someone to buy 3 and sell the rest on trademe. But why is the 19 range meter rated 1 star?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Simon Bayley on Friday, June 22, 2012 - 05:55 pm:

Kep,

I am in New Zealand - Christchurch to be exact and have brought two analogue meters from Jaycar www.jaycar.co.nz - they sell online and also at stores throughout the country.

Dick Smith has reduced their range over the years so try jay car instead.

Cheers Simon


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