Ask the Mechanic

June 2020 Steve's Back and Forth Hammer Works

(Progressive Farmer image by Steve Thompson)

STEVE: David Mitchell, from Byron, Michigan, has a problem with his old tractor that is still common today. See if you can diagnose the problem with David's tractor as his story unfolds:

READER: "I have a 1953 Massey-Harris 33, serial number 33GIRF2568. When I purchased this tractor five years ago, it had a motor knock. The knock was gradually getting worse. I had a mechanic take the pan off. The mechanic found that it had been overhauled, and the front main bearing halves were upside down, so the oil hole did not line up with the hole in the block. After a period of time, the tractor started missing and running very rough. I thought it was a carburetor problem. I decided to look at the ignition possibilities. I used a small hammer and tapped the underside of the distributor. To my surprise, the tractor smoothed out and ran correctly. But, after 10 minutes, the tractor started missing again. Again, I tapped the underside of the distributor, and again it stopped missing. This continued to happen, sometimes after only a minute of running. I decided to remove the distributor and check the points, condenser and weights on the timing advance -- nothing wrong. After reinstalling the distributor, the tractor acted the same way. The tractor to this day continues to repeat this frustrating problem. Can you help me pinpoint the problem?"

STEVE: It's that old ground problem. The distributor must be grounded, and the distributor on most tractors does not have a separate ground wire and must ground back to the engine block -- usually with the help of the hold-down clips. As we have all learned, if it is doing something crazy, it's probably a ground problem. I repeat what Pappy Thompson has always said, "Electricity won't leave unless it can come home."

> Write Steve Thompson at Ask The Mechanic, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email mechanic@progressivefarmer.com.

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