Howdy folks, My model T ran low on oil as the bendix cover came loose....The magneto started to play up and it missfired every time i switched it to mag from battery...when I put fresh oil in the engine it ran fine on magneto but i put 5/30 in it and it started to missfire after it warmed up....I am a very competent modern day car mechanic (37 Years) but not a great T mechanic as i am kinda new to them...does anybody know why running low on oil affects the mag and most of all what I have to do now to right it???? My T is a 1910 runabout with a 1917 motor and trans (with starter) also what is the best band material as I hAVE TO REPLACE MY 1ST GEAR BAND....Thanks in advance Joe o...ps. i cannot upload my t pictures on here either maybe someone can tell me how..
Check your mag contact post to see it it has a lint build up on it. This would cause it to have poor contact with the mag. and a miss.
As for band material you will get many opinions from wood to kevlar. I use kevlar and am happy with the result.
no the contact post seems fine (to me)
Just an idea? When the oil gets low, if your valves are a little tight (at least not loose), they can close slowly (often called valves floating). This reduces both intake and compression, and at different amounts in different cylinders depending upon which valve is floating how badly.
Why this would matter on mag more than battery. The mag fires a single spark at a very precise moment based upon the position of the magnets on the flywheel relative to the field coil. If this pulse hits when the cylinder isn't prepared due to the valve float, the cylinder may not fire or will fire badly. The battery makes multiple sparks beginning at the first moment of timer contact, continuing until contact is lost at the other end of the timer contact. If the compression comes up low and late due the the valve float? A late fire from the battery would still run better than no fire from the magneto.
I don't know that that is the reason, but it could be.
Is your motor okay after running low on oil Amazingly, often they are fine.
Drive carefully, and enjoy, W2
An un-optimistic possibility......Running low on oil allowed Babbitt wear on the thrust surface of the rear main. Excessive crankshaft end play can play havoc with magneto operation as the magneto gap opens and closes under varying circumstances. When the crank moves forward, the gap is nice and small and the mag operates properly. When the crank moves back, the gap opens and the mag becomes very weak.
Seems to me to be only co-incidental that changing the oil caused the engine to miss-fire.
Look for something causing the miss. Missing can be related to fuel supply too. Or intake. Or valve.
Most times its ignition caused.
Depends on the miss, does it do it at idle, or miss more at speed? Is the miss related to only one cylinder? Many things to check.
Run the T on battery DC voltage to determine if missing is only related to the mag. The coils should be checked too, as sometimes they wear and one or more could be missing now on magneto AC voltage.
Another possibility if you used graphite type oil it could cause shorts with the mag. Jim
It could be a co-incidence, or possible if your oil has graphite. To check for excessive endplay, push your low pedal down. That will move the crankshaft back away from the magneto coils. If it moves too far, it will lower the output of the magneto. You would notice this especially when the engine is running slowly such as idle or starting out from a stop or pulling a steep hill.
To check for excessive endplay, after you depress the low pedal, let the pedal out and go to the front of the engine with a large screwdriver insert between the crankshaft pulley and try to pry the pulley forward toward the radiator. Don't force it hard enough to bend or break anything. It should move quite easily forward if the crankshaft has endplay. It should only be a few thousandths play, not really noticeable with the screwdriver, but if you get enough to be noticeable, you have too much.
Your wear on the rear bearing thrust surface could have been borderline and the running low on oil could have caused just enough additional wear to make the difference.
Before you try any drastic measures, check the voltage output with an AC analog volt meter across a lightbulb from the magneto post to ground. It should be around 6 volts at idle increasing with engine speed to over 20 volts. If this is OK your magneto is working and the trouble is somewhere else. Clean your timer and check the coils.
If the magneto voltage is low you can still try the in engine recharge. See other posts to see how this is done. That could help.
Just another possibly- if you are like many, when you refilled the crankcase with oil, is it possible that one of the aluminum foil sealers under the oil can cap made it's way into the crankcase?
That little booger can find an invisible hiding place and cause a short. Check your oil bottles and make sure the foil seal is accounted for.
How do you know if your oil has graphite in it? I've never heard of such a thing, but I'm not an expert in oils. Is it listed on the bottle, or is there another way to check?
There used to be graphite engine oils sold by Arco, Cam2, Quaker State and many other companies. Most of them, if not all, were pulled from the shelves after Generic Motors sent a notice to dealers that warranty claims for failed engines would not be honored if those oils were used. I often buy motor oil at garage sales and have not seen any of the stuff lately but if I did I would not buy it.
There are still many phoney baloney oil additives on the market. Many of them still contain graphite like this one:
Easy way to avoid trouble - don't buy any oil additives. They are in general not worth the money and in some cases dangerous and harmful to your engine.