Lawn Tractor: Runs For A While Then Dies

Your lawn tractor’s carburetor mixes air and fuel to the proper mix for combustion. When fuel sits idly for a long time it can gum up the inside the carburetor. If your carburetor is clogged, you can take it apart, clean it, and use a carburetor kit to replace the internal parts. To remove the carburetor, first remove the air filter assembly and remove the carburetor bolts and linkages. Now, you can take the carburetor apart (we advise that you take pictures of the carburetor parts you remove with your phone so you can remember how all the parts fit in). Clean the inside of the carburetor with parts cleaner and re-install all the new parts. Now you can re-install the carb onto the engine. Next, locate both idle screws on the carburetor; one is marked L (low) and one is marked H (high). Turn both screws all the way in to shut off fuel, then turn them in the opposite direction 2 turns, and start the engine. The engine may not run perfectly, but it should start at these settings. Next, let the engine idle for 5 minutes. Start adjusting the carburetor by turning the L screw clockwise to add more fuel and set the idle. At full throttle, turn the H screw clockwise to set the high idle. When the engine runs well your carburetor is properly configured. Now you can re-install the air filter assembly and the air filter.

The air filter is located on top of the carburetor. Its main purpose is allowing clean air to flow into the engine and prevent small particles from damaging internal engine parts. Over time, the air filter will need to be replaced as it becomes clogged with small particles and debris, starving the engine of air. When the engine is starved of air it can die, even if it has run for a while with no issues. To replace the air filter, first remove the air filter cover. It may be attached by screws or just a tab, depending on the model of your tractor. Once the cover is off, remove the filter and replace it with a new one. This should be done regularly as part of your general maintenance routine.

The fuel pump is designed to pump fuel from the fuel tank to the carburetor. If the fuel pump is old, it may be weak and therefore it may not be able to keep up with demand when the engine has run for a while. To check for a bad pump, first locate the fuel pump and, if there is no shut off valve, pinch off the fuel line to prevent flow of fuel. Remove the fuel pump and check for damage. If the pump does not show any damage on the outside, you can then begin taking it apart. Remove the fuel lines, and the screws holding the pump together. Make note of where all the parts go inside (to do this, we recommend taking a picture with your phone), so you can re-assemble the pump properly. Check inside the pump for damage. Finally, clean the pump with parts cleaner and replace all inside parts with new parts, then re-install.

The gasket’s job is to prevent air and fluids from entering areas where they can cause damage and affect performance. A damaged gasket below the carburetor will allow excess air to enter the engine, and this can cause the air/fuel mixture to be wrong. This can result in a loss of power, and can also cause your tractor to die, even after it runs for a while. To check the gasket, start by removing the air filter and loosening the carburetor bolts. Once the gasket is visible, look for tears, rips, and any indications of leaks. The gasket will need to be replaced at this time, regardless of its condition, as they can only be used once.

The spark plug ignites the air/fuel mixture in the combustion chamber to power your tractor. A damaged plug can eventually fail to ignite the mix, which will cause the engine to die. To check the spark plug, first remove the wire from the spark plug, being careful when doing so as they are very fragile. Now you can remove the spark plug and check its condition. A good cleaning and re-gapping to the manufacturer’s specifications will usually solve this problem. However, it is usually a good idea to replace the spark plug, as they are inexpensive and they should be changed relatively often as part of regular maintenance. If the engine runs at high rpm a lot of the time, or is running under a heavy load, you will potentially require a cooler-running plug to dissipate heat more quickly. A hot-running plug will sometimes not fire if it overheats.

The ignition module produces the electrical charge for the spark plug. To check for a bad ignition module, attach one end of a tester to the ignition cable and ground the other end to the cylinder head, then spin the engine at least 350 RPMs and check for spark in the window. If the module fails this test, it will need to be replaced. To replace the ignition module, simply remove the wires and the mounting screws, and turn the flywheel magnets away from where they meet the ignition module. At this point you can install a new module. To do this, first tighten one screw, and insert a shim to set the gap (a business card will work). Then, turn the flywheel so the magnets meet the module (the module will pull itself to the magnets). Finally, tighten the screws and your repair is complete.D705