Stale Fuel

Every Spring we hear the same story. "It ran good when I finished tilling my garden last Spring". If you take the gas cap off, the odor almost knocks you off your feet. What has happened is the small amount of gasoline in the tank and carburetor has gone bad and in many cases turned into a varnish. This varnish clogs the fuel metering ports and causes the engine to run erratic or not at all. What's the best thing to do to prevent this from happening? Run the tank dry before putting it away? No! Not a good idea, the small amount of fuel left in the system can turn to varnish as it dries up. Here's what I usually recommend:

Gasoline is very dangerous. Work only in a well ventilated area, away from any source of heat or open flame!
  1. Treat the last tank of fuel with a gasoline stabilizer.
  2. Always put the engine in storage with at least a half tank of fresh treated fuel in it.
  3. Run the engine for 10 minutes after treating the fuel, so that the stabilizer gets into the entire fuel system.
  4. Start the unit up every month or two to keep fresh fuel in the carburetor during the season. Fuel does evaporate from the carburetor.
 The important thing to understand is that gasoline does not do well when stored in small quantities or open sunlight. If you don't use much fuel during the season, then try to keep what you have fresh and in a cool shaded area. Dump it in your car and get a fresh can every month or so. Most small engine shops sell gasoline stabilizer, as do hardware stores, etc. Fuel stabilizer will keep fuel fresh for two years.

If you already have the stale fuel problem, then start by cleaning as much of the old fuel out as possible, then with fresh fuel in the tank, try starting it. If it won't start or runs erratic, it's a trip to the repair shop. Or have a look at Two Stroke Engine Troubleshooting if your engine is a two stroke. So, let's keep that fuel fresh.

 

Also see Step by Step Two Stoke Carburetor Rebuild, Complete Engine Rebuild,  Carburetor Rebuild, Loose Valve Seats  Starter Rope Repair,        Carburetor Troubleshooting Chart or My Engine Won't Start for more troubleshooting.

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