Ask The Mechanic

Stabilize Fuel

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Q: Do you think a fuel stabilizer works? I have a hard time starting my line trimmer after it goes unused all winter. I have heard that leaving fuel in a small engine carburetor all winter long is not good for any part of the fuel system.

A: Yes, I recommend fuel stabilizer for winter storage. It will keep the fuel “fresh” all winter, but if the fuel in the tank contains ethanol, which is pure alcohol, it can still be destructive on fuel system parts, including the fuel line and the diaphragms in the carburetor. I have personally found that the best way to store a small engine for winter is to pour out all fuel in the tank and run the engine out of gas. Since it’s generally impossible to completely evacuate the system of fuel, what works best for me is to pour just enough “canned” fuel that is free of ethanol in the tank to run the engine. This “canned” fuel is available at all lawn and garden equipment outlets.

This fuel mixture will never plug your fuel system, and it will not “go bad” all winter long. So, next spring when you try to start your line trimmer with bad gas in it, your spouse won’t have to ask you, “What is that smell?”

Q: I am converting my 24-volt 4020 to a 12-volt system. This 24-volt system is driving me insane. Are the lights on the dash that show oil pressure and charge 24-volt light bulbs? Are the lights in the fenders 24-volt, as well? I’ve been looking for 24-volt lights, and they are not readily available. Everyone keeps telling me to go to a military surplus store because the military sometimes used a 24-volt system. The John Deere dealer tells me he doesn’t stock 24-volt lights but says my tractor is a 24-volt system. I’m in the dark on this one.

A: Let’s see if I can shine a little light for you. The electrical wizards at John Deere set up the 24-volt system so that it went to 24 volts only when the starter was engaged. Older diesel engines had a bad reputation of cold-weather starting, and a starter running on 24 volts requires half as much current to turn the same load as a starter running on 12 volts. That’s why it is more economical to use a 220 grinder in your shop rather than one that runs on 110.

Now, we need to go back to your tractor. Each side of the tractor runs on one battery, so that allows each bulb to be a 12-volt bulb. Since each side had to be balanced on current use, it was important to keep all the bulbs burning the same on each side. And, get this one: When the cab was put on these tractors that had a 24-volt system, the blower motor was 12-volt.

In order to keep the batteries up, the tractor operator had to toggle a switch running the blower motors back and forth from one battery to the other during the time of operation; otherwise, the system would be unbalanced, and one battery would eventually go dead. When John Deere switched to the 12-volt system in 1969 on the 20 series, it was welcomed by all--dealer, technician and tractor owner.

Safety Tip of the Month:

When hooking to a drawn implement, always be careful when standing between the tractor and the implement if the tractor is running and a driver is on the tractor. If the tractor is in reverse, one little slip of shoe on the clutch pedal can cause serious injury, even death.

My friend was helping me hook up to a disc one weekend. I was trying to drop the hitch pin as he backed up the tractor. All of a sudden, a nest of bumblebees attacked us. He instinctively released the clutch as he was stung. Had I not already been running away from bees, someone else would be writing this article.

Write Steve Thompson at Ask The Mechanic, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email


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