Troubleshooting a Stalling Cub Cadet Engine

It is always an unpleasant deal with a mechanical failure of any kind, but during the winter months, when you really need your equipment to be functioning, it can be life threatening if your small engine fails to start. Thankfully, if your Cub Cadet small engine does stall or otherwise fails to start when you expect it to, there are a number of simple checks you can perform to determine exactly what the problem is and how to fix it. Many of these checks are applicable to all small-engine lawn and garden equipment, so properly educating yourself can save a lot of time and headaches when you are presented with a problem!

Before you attempt to diagnose the problem, there are a few things you should always have on hand to fix the most common, most easily solved quandaries.

  • Clean Air Filter:  It’s easy to forget that engines require air just as much as they need gasoline, necessitating a clean air filter; inadequate air supply will prevent combustion, meaning a non-functioning engine.
  • Fuel: Fuel can go stale as readily as the milk in your refrigerator, as the more volatile components evaporate into the air and some of the chemicals in the fuel oxidize to become less reactive (and emit a foul smell). Any water that finds its way in might bring with it a number of contaminants that effect how well it burns. Depending on storage conditions, gasoline can go bad in as little as 30 days.
  • Finally, keeping a new spark plug on hand can save you a trip to the hardware store at the most inopportune time.

If you do not have these materials, it might be harder to diagnose the exact reason your engine is stalling, simply because you cannot substitute the new materials in for the old to see if the problem gets fixed.

There are six common problems that might be the culprit behind your stalled engine:

  1. Use of old fuel – old gasoline, whether it was sitting in the unit for a long period of time or resting in a gas can in your garage, may have been exposed to a number of contaminants that decrease its efficiency, the volatile chemicals that help kick-start the ignition process might have evaporated, and some of the necessary hydrocarbons could have oxidized. Change the suspect fuel completely.
  2. Carburetor varnished – usually caused by leaving fuel in the system for too long, and a possible culprit if the introduction of fresh fuel did not help. The metering needle and the fuel lines may become clogged or glazed with the old fuel, which tends to become sticky (like varnish) and blocks a proper air mixture from forming. Unfortunately, a cleaning of the carburetor and even a rebuild are the only solutions.
  3. Spent spark plug – over extended use, spark plugs will form carbon deposits that block a proper spark from forming. Replacing the spark plug periodically will get it flaring properly again.
  4. Faulty air filter – filters tend to become too dirty to function over time, simply because they are performing their intended function of filtering undesirable particles from the air used in the engine. In addition to replacement as part of routine maintenance, be especially careful when tipping any small engine. Oil is liable to leak onto the air filter, clogging it up in a hurry. Always try and keep the air cleaner pointed up when moving the engine, and replace it if it is too clogged to function.
  5. Debris in the carburetor – this kind of debris can come from almost anywhere and block the fuel to the carburetor. Metal gas cans, for instance, might rust slightly on the inside, and a speck of rust falls off into the gas tank of your engine as you refill it. You can test for this easily by checking for fuel on the spark plug after pressing the primer. If none is present (i.e. you cannot see any wetness nor smell gasoline) the fuel passageways are most likely obstructed.
  6. Ignition coil failed – the rarest of these potential causes of your engine stall or start-up challenge. To test this properly, you need a spark plug testing took available at most hardware stores for a few dollars. The tool allows you to safely and efficiently test to see if a spark is created at the spark plug terminal – if you are using a new spark plug and there is no spark, there is no electrical activity and the ignition coil has most likely failed. There is no remedy but to replace the coil.

If these tests do not solve the problem, you most likely need professional help to fix your engine. Cub Cadet highly recommends OEM parts only. While OEM parts may be more expensive than some off-brand parts that claim to be alternatives, results on the cheaper parts are usually questionable at best. Compatibility issues with the machine you install them on are very common, and they tend to fail faster than official alternatives.

Purchase your OEM parts online at Use their online parts diagram to locate the part that you need, choose the shipping and payment options and the part will conveniently be delivered to your door.

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