Revive Your Cold-Blooded Engine

Storage presents unique challenges to gasoline engines that power landscaping and turf equipment, especially when the storage exceeds 60 days. While a hard-to-start engine can be frustrating, almost anyone with a basic mechanical aptitude can successfully troubleshoot most common starting problems.


Often, the ability to start an engine following storage is directly impacted by the equipment's preparation prior to storage. Diligent performance of simple maintenance items such as fully draining the equipment's fuel system, replacing the fuel filter (if so equipped), changing the oil and oil filter (if so equipped) and cleaning the air filter prior to storage in the fall will ensure it is easy to start in the spring. Manufacturers often post recommended service schedules for engine or equipment models on their Web sites. Your equipment dealer is also a great resource for pre-storage preventative maintenance information.


If an engine doesn't turn over, the first mistake some people make is to assume it's an engine or battery problem. Modern equipment is made up of several inter-connected systems, of which the engine is only one component. A commercial mower, for example, has several interlock switches that can prevent the engine from starting. One of the first troubleshooting steps should always be to ensure each of the equipment's interlock switches is functioning properly, and is in the proper position to allow the engine to start.

If the engine does not turn over after checking the interlock switches, test the battery for proper charge and visually verify that the battery is in good condition. Clean up corrosion around the battery connections and inspect battery cables to verify they are secured properly.

If your interlock switches are functioning — and your battery, battery cables and connections are good — and the engine still doesn't turn over, you're likely facing a bigger issue with either the starting system or the overall electrical system. Either way, it's best to have a factory-trained technician give the equipment a closer look if you get to this point. In addition to assisting you with further troubleshooting, your dealer can provide you with a wiring schematic for the equipment.


If the engine ran when it was put into storage and turns over when it comes out of storage, my experience tells me there is about a 90-percent chance the starting problems are related to one or more issues within the fuel system. Whether the cause is gumming and deposits from old gasoline in the carburetor, a clogged air filter, an improperly functioning choke mechanism or a combination of issues, most of the starting issues service technicians see are fuel system related.


The first, most basic check to perform on the fuel system is to verify that the piece of equipment is fueled with the proper fuel (gasoline, in this case), and that any fuel shut-off mechanisms are in their ON or RUN positions. Assuming these two criteria are met, and the engine still doesn't start, you will need to start investigating deeper within the fuel system in your search for answers.

Fuel age and seasonal gasoline formulations can quickly make an otherwise good engine difficult to start. Storing equipment with untreated fuel in the tank for more than 60 days is risky, as aging gasoline can cause havoc within the carburetor and other fuel system components. “Old” fuel is usually easy to identify because it carries a varnish-like odor. The presence of this smell is often an indicator of other issues in the fuel system that you will need to examine before the engine will start or run efficiently. As fuel ages, gum and varnish-like deposits form within fuel system components, preventing fuel from being able to flow through the carburetor.

If you think you smell varnish when you open up the fuel tank, you will need to drain the fuel system completely. It might get to the point where you need to completely disassemble the carburetor and other fuel system components and clean the parts with an aerosol-type carburetor cleaner. You should reassemble the carburetor using a carburetor rebuild kit, which is readily available from each engine manufacturer for its respective models.

Seasonal gasoline blends can also cause starting issues, especially where there is a significant temperature shift between the seasons. For example, in midwestern states, fuel blended for summer use will make an engine hard — if not impossible — to start in winter or early-spring weather conditions.

Because of these variables, you should completely drain fuel from the fuel system and run the engine until the fuel is exhausted if you're storing equipment for more than 60 days. This keeps harmful gum and varnish from building up inside fuel system components during storage, and guarantees the engine will receive the appropriate seasonal blend of fuel for the conditions by requiring fresh fuel when it's removed from storage.

In circumstances where equipment will be stored for more than 60 days with fuel, use a fuel stabilizer. Fuel stabilizers have additives that prevent gumming and residue that can result from fuel evaporating inside fuel system components during storage. They also give fuel characteristics necessary to ensure startability, even after extended storage periods.

Once you have determined fuel type or age is not the issue, you should inspect the fuel system to ensure they are clean and functioning properly.

  • Verify the choke and/or primer bulb system is working properly.

  • Check the carburetor anti-afterfire solenoid for proper function (if so equipped). Designed to stop the flow of fuel immediately when the engine is shut down, the anti-afterfire solenoid prevents fuel flow into the cylinder of a hot engine after the key has been turned to the OFF position. The easy way to test this is to listen for an audible “click” from the carburetor area when the key is turned from the OFF position to the RUN position.

  • Check the air filter. Is it clean and maintained properly? If the filter becomes plugged with fuel or contaminants, it becomes saturated and will not allow sufficient air to pass through to create the proper fuel/air mixture.


If everything checks out with the fuel system and your engine still won't start, focus troubleshooting efforts on the ignition. Because the ignition system is responsible for the spark that ignites the fuel/air mixture, without proper spark, the engine will not start.

Anytime you suspect a lack of spark is the problem, replace the spark plug(s) right off the bat to ensure that a plug fouled by oil or fuel isn't the cause of the starting problems.

If you replace the plugs and the engine still refuses to fire, you should verify the ignition module is generating sufficient voltage to produce a spark using a spark tester. Some people will test a spark by simply removing the plug and laying it against the cylinder fins to ground it. This is not a good idea. First, it's nearly impossible to get an accurate reading of spark quality, and second, it is just plain dangerous. The fuel vapor that goes into the cylinder gets blown out through the spark plug hole, creating a potentially hazardous situation.

Dedicated spark testers are typically available for less than $15, and simulate the electrical load placed upon an engine during operation. The spark tester is designed so that, if a spark appears in the tester window, you know the ignition is capable of producing sufficient voltage to start your engine.

If no spark is produced, check for improper ignition system grounding by disconnecting the engine stop switch wire directly from the ignition armature, which is typically located next to the flywheel under the blower housing. If a spark is produced when the stop switch wire is removed, it is an indication of improper grounding of the armature. It is also very important for the armature to mount cleanly to the engine block, in the proper orientation (not backwards), with the proper gap between the armature and the flywheel.

To keep your business up and running throughout the year, take the correct steps to ensure that your equipment doesn't face any downtime for repairs after it has been in storage. By taking care of your engine at the end of one season, you guarantee that it will live to see the next.

Mark Nelson is a product service trainer with Briggs & Stratton Commercial Power (Milwaukee, Wis.) and has worked with commercial engines for more than 25 years.

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