How to Troubleshoot a Diesel Lawn Mower

Check the fuel level in your diesel lawn mower. Refill your tank if you are out of fuel.

Use the cold start lever of your diesel lawn mower, if your model supports it. This releases the hydrostatic transmissions from the starter cranking load, and should be used if available in weather below 40 degrees Fahrenheit.

Start the diesel lawn mower in cold weather with the throttle beyond idle -- 1/4 to 1/2 throttle. This helps the mower start if it is struggling to ignite in cold weather.

Open the front engine hood of the diesel lawn mower and ensure the black ignition wire is connected to the spark plug on the side of the engine.

Disconnect the ignition wire from the spark plug if it was already connected but the spark plug appears faulty. A faulty spark plug may exhibit brown or black corrosion on its end, may appear worn, or may feature blistering on its white insulator ring. Remove the old plug if it meets these conditions.

Reinsert the ignition wire into the rear of the replacement spark plug.

Ensure the red positive and black negative battery wire's are connected to the bolts on the top of the diesel lawn mower's battery. Use a socket wrench to tighten them back over these bolts if necessary.

Change your oil and your oil filter if problems with the diesel lawn mower persist. This is necessary after every 100-200 hours of operation. Find the oil filter and drain plug locations on the left side of the engine assembly. Remove the dipstick.

Unscrew the oil fill cap and pull the drain plug out to drain the old oil into an oil pan for disposal.

Remove the oil filter and wipe off the diesel engine's filter mounting surface with a soft cloth.

Put a thin coating of new oil onto the replacement oil filter's gasket.

Slide the filter onto the area vacated by the old oil filter, turning it clockwise until the gasket makes contact with the sealing surface. Tighten it an additional half turn.

Reinsert the drain plug and tighten it into place.

Fill the engine's crankcase with clean oil that fulfills the specifications set forth in your particular model's owner's manual. Fill the crankcase only far enough that it reaches the dipstick's upper mark.