Troubleshooting Model Airplane Engines

Battery type and priming

If the engine is firing intermittently, most likely it could be a problem with the battery type. Checking the recommended voltage for the model airplane's engine ensures that the correct battery is being used. When the engine fires intermittently, the cause may also be too much priming of the engine. This is resolved by removing the battery and allowing the engine to rest. Five minutes will suffice. Run the engine again. If the problem persists, the fuel is drained from the engine by removing the gas cap and oscillating the propeller.

Fuel troubles

Fuel problems tend to be the most obvious difficulty with a model airplane engine. For example, if the revolutions per minute (RPM) decrease after the engine starts, the engine will shut down. Engine shutdown is typically a sign of the tank being over fueled. The fuel itself may be a problem (perhaps, the mixture is too rich). To remedy this, the needle valve is closed (about half a turn). The engine is then restarted. If the RPM increases after the engine has started, and then the engine cuts off completely, then the fuel is not reaching the engine. The fuel tank is checked to ensure it is filled up, and the carburetor is checked for dirt clogging (It is also advisable to check the tubing of the fuel for any cuts or breaks).

Engine stops after battery is removed

If the engine starts but stops completely after the battery has been removed from the system, you're looking at fuel mixture issues (or too much fuel). To fix this problem, the needle valve is slightly closed. The glow plug may not be compatible with the fuel type for the model airplane's engine. Either way, the fuel type or the plug must be changed (see manufacturer's manual).

The engine doesn't start at all

When the engine doesn't fire up, the propeller may have been feebly rotated. To remedy this nuisance, give the propeller a heftier spin. As is often the case, other components may be the cause of the engine not starting. The battery may be low on energy (recharge the battery or replace with a new one). Engine flooding is resolved by removing the fuel plug, rotating the propeller and allowing the fuel to drain entirely. Model airplane engines use a glow plug rather than an ignition starter. If the glow plug is burned out, you must replace it with a new one.