i own a 27 roadster and the last couple of times ive run it, after shuting it off, say for a minute i turned the switch on it started up on its own whats the deal, at least i had retarded it back after shutting down ????????
You got a "Free Start". A lot of guys would love to be you. Yes, it's normal for a lot of T's. What's happening is, When you turned the key back on, the timer was in a position to make contact and start buzzing a coil, hence firing a plug. You had enough air fuel mixture in that cylinder to ignite, and VOILA! A free start. Some seem to do it more than others. It also seems to do it better if you rev it a little while shutting it off to get a good full charge of fuel in there. I've gotten mine to do it 12 times in a row. Other times it won't do it at all.
If I rev my '17 before shutting it off, it backfires and blows the muffler off (I've done that twice and had to buy a new muffler!). I have to fully retard my spark and throttle before shutting it off to keep it from backfiring. Why?
There could be a few causes. By all means check your intial timing to make sure it is right but also you might check your ignition switch. It could be that it is intermittent and when shutting it off it might be making a momentary "Make/Break/Make" that shuts off then turns back ON the ignition for just a moment during the shut down and allows the cylinder to charge up and dump some raw gas into the exhaust and then light it off. Mixture setting might aggravate the problem too somewhat. Others may have different opinions. I personally have never had a car do that but I have watched guys deliberately make their T backfire by turning off the ignition while the engine was spinning pretty good and then turn it back on rather quickly after that - result - BOOOOM!!
I did that a few years ago just after passing a local officer with a car pulled over. He followed me home and sternly asked me not to do it again since they have reports of "shots fired". He also mentioned something about "disturbing the peace"!!!Someday, I'll grow up!
A rich mixture on a hot manifold could cause that problem. Let the car idle before turning it off. If you turn it off while it is running fast, it will draw more fuel in and then go out the exhaust valves to contact the hot manifold and BANG!
I had a similar FREE START when cranking the car. The battery was dead and I choked it too much which flooded it. To un flood it, I turned off the ignition switch and with the throttle open full, I spun the crank a few times to draw in air. Then I went around and turned on the key, and it started! I don't know if my audience quite understood what had just happened or not.
That's what I do with the '26, and don't have a problem. But unless I retard the spark and throttle all the way on the '17 (and wait until it practically stalls), I get a backfire when I turn it off. Otherwise, it cranks/starts easily and runs perfectly.
Free starts are natural, and in most cases indicate a well adjusted, tuned engine. Some cars had a "button" you could push (our 1910 Oakland had one) that "fired" all four cylinders. Then, if one was "on compression" with fuel, it would fire, and start the car (free start).
I find that if I pull down the fuel lever, just as I shut off our Ts (and N, and Buick), then turn on the key, if I retard the spark slowly, I'll catch a spark, and start the car with a "free start". A variation of this is when you choke, or just crank a few times with the ignition off (to "prime" the car), then try for a free start, you'll frequently get it.
My Grandpa told me he used to have his Model T so well tuned that he could set the levers just so and impress his friends by cranking it with a good, swift kick to the tire. Just prior to this, he would have to do a little preparatory work and prime the cylinders by turning over the crank with the key off. The kick would cause the spark lever to jostle down to the next timer/coil contact, activating the coil spark that would cause the car to roar to life. I have never been able to do it with mine, but I can imagine it would be quite impressive. Jim
thanks alot for the info. it has just started up by it self when i have turned the key back on. never back fired like some of the other post even though i used to do that back in the 60.s on my motor scooters cushman ,allstate ect.
Idling with the spark all the way up is a way to heat the exhaust manifold, because the spark fires late, and some fire goes out the exhaust valves. That is also a potential cause of burnt exhaust valves. After starting the engine the spark should be advanced at 1/3 way down. Farther when driving. If you drive with the spark too far retarded the above also applies and you will notice a loss of power.
Reving the engine just before turning off the ignition leaves raw gas in the cylinders which will wash off the oil and will lower the compression as well as give a "dry start" Some people are of the false impression that it will splash oil up into the cylinders and it will start easier. Maybe that would be true if one were to start it up soon after turning it off, but if you let it set for weeks at a time, most of that oil will drip back into the crankcase anyway. Best to idle it with the spart partway advanced prior to shut off.