Most Toro lawn mowers have a four-cycle engine, and like all internal combustion engines, they need three things to operate: fuel, spark and air. If you're having trouble starting your Toro lawn mower, a few simple procedures may get you mowing quickly, even in the wake of a long winter during which your mower was in storage. In the worst case, you may have to spend some time draining the tank and cleaning the carburetor.
Use the Proper Starting Procedure
Before you suspect problems with the lawn mower, check your owner's manual to make sure you're using the proper starting procedure. Most Toro lawn mowers have a priming bulb, and the manufacturer recommends pressing it three times before pulling the starting cord or turning the key on electric-start models. If the temperature is below 55 degrees Fahrenheit, you should press this bulb five times. It's also important to hold the blade control lever against the handle. This lever engages a brake when you release it, and the mower won't start unless you squeeze it next to the handle to disengage the brake.
Check the Plug, Filter and Battery
A dirty air filter prevents air from getting into the carburetor. To clean the air filter, locate the filter compartment with the help of your owner's manual and follow the instructions to remove it. Clean it with soap and water or replace it. You should also remove the spark plug, using a spark plug wrench, and clean it or replace it if necessary. If the plug is fouled with black carbon deposits, it's an indication of inefficient fuel burning, probably caused by a dirty air filter or bad gasoline. If your lawn mower has an electric start feature, charge the battery for the amount of time recommended in the product manual.
Change the Fuel
It takes about 30 days for fuel to degrade, so if your lawn mower has been in storage for the winter with gas in the tank, there's an excellent chance that the gas is bad. Gasoline collects moisture as it sits, and because water is heavier than gasoline, it sinks into bottom of the tank, where the fuel intake is located, and enters the carburetor when you try to start the engine. Drain stale fuel into an approved container for disposal, and before refilling the tank with fresh fuel, crank the engine several times to clear the carburetor.
Try Starting Fluid
If your Toro lawn mower won't start after following these routine procedures, the carburetor may be blocked with varnishes that accumulate from stale fuel. You can quickly dissolve these with starting fluid; besides being highly flammable, it is also a strong solvent. Remove the air filter and spray a one-second squirt of starting fluid into the carburetor through the air intake, then crank the engine. If the engine sputters but doesn't start, spray more starting fluid and try again. Replace the air filter as soon as the engine turns over. If you get no response at all, it's time to take the mower to a service pro to have the carburetor cleaned.