Back firing want start but will hit

If your lawn mower begins to backfire and does not start, it is most likely due to a faulty fuel system. It`s possible that the gas is old and has gone bad, or that there is water in the tank. In either case, you`ll need to drain and replace the fuel in the gas tank.

Fuel and Speed Issues

Stopping the engine of your mower abruptly without reducing the engine speed using the choke may cause fuel to pump through the engine, causing it to backfire. A hot muffler and gasoline with a high alcohol content may cause the engine to backfire, also.

This can be caused by a faulty mass airflow sensor or a clogged engine air filter “choking” the engine and not allowing enough oxygen to flow into it. Or, it could be caused by leaking fuel injectors forcing too much fuel into the engine.

Loose, Dirty or Disconnected Spark Plug in Your Lawn Mower: Check it out, clean off debris, re-connect and tighten. Dirty Air Filter: Clean or replace. Fuel Not Reaching the Engine: Tap the side of the carburetor to help the flow of gas. If this doesn`t work, you might need a new fuel filter.

Excessively lean carburetor settings can contribute to backfiring. If the mixture is too lean, it may burn very slowly and unevenly. This condition, in turn, may result in burning mixture remaining in the cylinder until the beginning of the next intake stroke when it can ignite the incomming air/fuel mixture.

It could be the spark timing is off. The plug may be sparking too early or too late. If this is the case, the backfiring is caused when residual fuel is ignited at the wrong time. A simple two stroke uses a magneto or a curved iron bar in the flywheel that spins by a copper coil to generate the spark.

If the spark plug of the lawn mower engine is compromised, then only a weak spark will be created, leading to constant backfiring. Gasoline is not ignited in the fuel chamber; instead, it ignites when the gases reach the muffler chamber.

Backfires and afterfires are worth paying attention to since they can cause engine damage, power loss, and decreased fuel efficiency.

Bad Ignition Timing

However, if the spark timing isn`t just right, the spark could fire too early before the intake valves are closed, or too late when the exhaust valves have already opened. When this happens, the air/fuel mixture in the exhaust or the intake can combust, leading to a backfire.

If your lawnmower is starting and then stalling, the most likely issue is the carburetor. The most common issue is that the carburetor is dirty. Here`s what you need to know about how a dirty carburetor can cause a lawnmower to start, then stall out and die.

If the spark plug of the lawn mower engine is compromised, then only a weak spark will be created, leading to constant backfiring. Gasoline is not ignited in the fuel chamber; instead, it ignites when the gases reach the muffler chamber.

Clogged or Dirty Air Filters

Dirty air filters are one of the most common reasons lawn mowers sputter. Dirt can be present in the apertures that lead from the carburetor and the fuel filter and interrupt the flow of fuel supply to the combustion chamber. You want to be sure to clean or replace dirty air filters.