Stopping the Engine

F-12 Farmall Tractor

September 1, 1993: F-12 Farmall, FS 103311, as found near Jackson, Mississippi. The owner said a neighbor ran it belted to a corn crusher (hammer mill) without oil and burned up the engine. The rear sleeve was cracked, and the block was cracked in four pl

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1905 Ridgeway Lane Hattiesburg, Mississippi 39401

For several years the hobby of restoring gas engines and tractors has directed my attention to how to get them restored and running. Little attention is given to stopping them.

Last week I cranked a restored 1936 F-12 Farmall and a neighbor was almost as excited as I was! We let it run a few minutes and retarded the magneto to stop the engine.

The next morning, the neighbor and a few others drifted by to see the completed tractor and hear it run. The spark was advanced halfway, gas turned on, governor lever pulled back, choke applied, can removed from the exhaust, and I started pulling up on the crank. What happened next? You guessed it. It did not crank! I monkeyed with everything on it and cranked some more. All new guts in the engine, new Champion spark plugs, reworked magneto, it was running 12 hours ago, don't leave me now neighbors; it'll crank soon! After a few more blisters on my hand, the neighbors drifted away, leaving me almost dead from exhaustion and embarrassment, and all alone with a pretty, red, dead tractor.

It must be the magneto is not hot enough. I removed the magneto that was running the 10-20 McCormick Deering and installed it on the F-12. Still no crank. The carburetor was re-moved and gone through again. This did not work.

After the evening meal, a brief stir was made in the day's mail delivery and there was the Gas Engine Magazine dated October. Before bedtime, I got to page 14 and read 'Some 'Tricks' of the Hobby' by Ed G. Page. I reread what he said about spark plugs. (Thanks Ed, you solved my problem).

The next morning I installed some old, clean plugs, and the tractor cranked on the second pull of the crank. I dried the new plugs with a propane torch, and they worked.

My next restoration will be a wartime flywheel crank John Deere B, built in 1942. To change color for a while, I started reading the operators manual for John Deere B tractor, serial No. 60,000 to 201,000. This covers about the years 1939-1946. Page 20 gives us what we have been looking for on stopping an engine. Page 20 concludes, and I quote:

'Caution: Do not stop the engine by pulling back on the hand throttle or by shorting the magneto. This leaves several charges of unburnt fuel in the cylinder, which will reliquify as the engine cools and permit the liquid fuel to lay on the electrode and porcelain of the spark plugs to provide a path for the spark to escape and result in hard starting. Liquid fuel left in the combustion chamber will also wash the lubricating oil off the pistons, rings, and cylinders, thus breaking the oil seal and causing poor compress on also a factor in hard starting.'

There you have it. It's in the book.

It stands to reason that when the ignition is stopped on a running engine, the flywheel keeps the engine in motion for a few strokes, pulling in fuel that does not burn, and saturating the spark plugs.

The lesson learned: Shut off the fuel and let the engine die naturally. It will crank tomorrow!