Operating Small Four-Cycle Engines in Cold Weather

Save time and money by preparing your snowthrower properly for winter.

Starting a snowthrower in winter can be time-consuming and costly for grounds maintenance professionals if you haven’t winterized the engine properly.

With preparation and preventive maintenance, you can improve the chances that your engine will start easily in cold weather. That will help improve productivity and, ultimately, increase business profitability.

A fresh start

Filling the tank with fresh fuel is probably the most important step in winterizing a snowthrower. Fuel has an extremely short shelf life and, therefore, you should not use it after 30 days—unless it has been treated with a fuel stabilizer.

The formulation for unleaded gasoline is changed several times a year to maximize easy starting in winter and to prevent vapor lock in summer. Cold-weather fuel has a higher Reid Vapor Pressure (RVP) than warm-weather fuel. To obtain the best-starting performance, don’t use use fuel purchased before fall in your snowthrowers.

When filling the fuel tank, start by cleaning the area around the cap. Make sure you clear all snow from the area to avoid contaminating the gas with water. Then remove the fuel cap and slowly add the fuel, using a funnel to prevent spills. Do not fill the tank to the top. Allow a 0.5-inch space below the bottom of the filler neck for fuel expansion after the engine warms. Once you fill the tank, replace the fuel cap and wipe any spilled fuel off the snowthrower.

Adding a stabilizer will help prevent the gasoline from deteriorating. Add the stabilizer to the fuel storage canister, then add the stabilized fuel to the engine fuel tank. After adding the stabilized gasoline to the engine fuel tank, run the engine five to 10 minutes to ensure that the entire system is treated, including the carburetor. It is important to note that although a fuel stabilizer will preserve fresh fuel, it cannot rejuvenate old fuel once it has deteriorated.

Maintenance matters

Preventive maintenance on a snowthrower also will maximize easy starting in winter. Inspect the snowthrower’s spark plug. Spark plugs generally need to be inspected seasonally and replaced after every 100 hours of operation.

Before inspecting the spark plug, clean the area around the spark plug base. Then remove and inspect the spark plug closely. If electrodes appear pitted or burned, or if the porcelain is cracked, replace the spark plug. Consult your owner’s manual to choose the correct spark plug.

Check a snowthrower’s engine oil. To check the engine’s oil level, position the snowthrower so that the engine is level. Clean around the oil fill cap. Then remove the oil fill cap/dipstick. Wipe the dipstick clean, insert it into the oil fill hole and tighten it securely. Remove the dipstick again. If the oil does not reach the “full” mark on the dipstick, slowly add the recommended amount of oil. When finished, wipe up any spilled oil. Be careful not to overfill the engine with too much oil.

You should change the engine oil after a snowthrower’s first two hours of operation and then after every 25 hours of operation. To change the engine oil, clean the area around the oil drain plug, and position the equipment so that the oil drain plug is the lowest point of the engine. Drain the oil by removing the oil drain plug and the oil fill cap. Oil is difficult to drain in cold weather. Running the engine five to 10 minutes will help facilitate draining.

Once the oil is drained, replace the oil drain plug, and fill the engine with the recommended oil. SAE 5W30 multi-viscosity oil is specifically formulated for operation below 32°F.

When finished, replace the oil fill cap, and wipe up any spilled oil. Discard the old oil in accordance with local regulations.

Operator’s checklist

Always read your engine and snowthrower operating manuals before using a snowthrower. You also should run through the following checklist before starting your equipment. Make sure that:

  • All control levers are in the neutral position. This will disengage all clutches, belts and chains and should place any safety switches in the safe-starting position. (Be sure you follow the equipment manufacturer’s instructions).
  • All nuts, bolts and attachments are securely attached and drive belts are in good condition. Most snowthrowers contain two drive belts.
  • The tire pressure is adequate. Improper tire pressure can affect how well a snowthrower scrapes snow off the ground. Consult your owner’s manual for the correct tire pressure.
  • The spark plug wire is attached to the spark plug and, if applicable, the fuel valve is open. The engine will die prematurely if the fuel valve is closed.
  • The ignition switch is in the “on,” “run” or “start” position, or the ignition key is inserted into the ignition key slot.

Furthermore, never tamper with the snowthrower engine’s governor, which is set in the factory for the proper engine speed. Overspeeding the engine above the factory high-speed setting can be dangerous and could shorten the life of the equipment.

Successful starting

If a snowthrower engine is properly maintained and filled with fresh fuel, it will frequently start on the first pull. Of course, how fast and how hard the operator turns over the engine also affects successful starting.

To start a snowthrower with a recoil starter, move the equipment- or engine-control lever to the “fast” or “start” position. Then move the engine choke to “full,” and push the primer two to three times. Grasp the starter handle, slowly pulling the rope until it becomes taut. Let the rope gradually rewind. Then pull the rope again—only this time with a rapid, full-arm stroke—allowing it to slowly return to the starter.

If the recoil starter is frozen and unable to crank the engine, pull as much rope out of the starter as possible. Then release the starter handle and let it snap back against the starter. This should free up the mechanism.

When the engine starts, gradually move the choke to “off.” If the engine then falters, immediately move the choke back to “full,” then gradually to “off.”

Starting a warm engine differs significantly from starting a cold engine. When restarting a snowthrower after a short shutdown, leave the choke in the “off” position, and prime the engine once.

Many of today’s snowthrowers are equipped with 120-volt electric starters, which simplify starting in severe winter weather. To start a snowthrower with an electric starter, first connect the power cord to the switchbox. Then plug the other end of the power cord into a Ground Fault Interrupted (G.F.I.) three-wire grounded 120-volt AC receptacle.

Snowthrowers with electric starters do not require priming. To crank the engine, simply push the starter button, or turn the ignition switch key, after moving the engine choke to “full.” When the engine starts, release the starter button, and gradually move the choke to “off.” Lastly, disconnect the power cord from the receptacle, followed by the switchbox.

Never run a snowthrower indoors or in enclosed, poorly ventilated areas. Engine exhaust contains carbon monoxide, a deadly, odorless gas.

Always keep your hands, feet, hair and loose clothing away from any moving parts on the engine or equipment. Do not leave a snowthrower unattended while the engine is operating.

Caring for engine controls

Protecting a snowthrower’s engine controls is another way to maximize easy starting and minimize downtime in winter. To help prevent the engine controls from freezing, take the following preventive measures after operating a snowthrower.

  • Wipe all snow and moisture off the engine near the control lever and choke.
  • Move the engine-control lever back and forth several times (see equipment manufacturer’s instructions). Then place it in the “stop” or “off” position.
  • Move the engine choke back and forth several times, leaving it in the “full” position.

Grounds maintenance professionals who prepare their snowthrower engine for winter will maximize easy starting, improve employee productivity and extend the life of the machine—all of which lead to increased business profitability.

Miles Geringer is product manager for utility engines at Tecumseh Products Co. (Grafton, Wis.).

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