Judging the Timing of Fuel Injection in a Single-Cylinder Diesel Engine

Most agricultural machinery is powered by diesel engines. The timing of fuel injection (injection advance angle) is crucial; too early or too late injection significantly impacts power output, fuel consumption, and normal operation. To ensure proper fuel injection timing, it's essential to understand how to judge whether the injection time is too early or too late for correct adjustments. Here are two simple methods for judging this.

For single-cylinder diesel engines, at the moment the throttle is closed and the engine is shut off, you'll often see either the fan or flywheel reverse or immediately stop rotating. This can help you determine whether the fuel injection timing is too early or too late.

When the fuel injection timing is too early, the air-fuel mixture forms prematurely and ignites prematurely. The expanding gas exerts a counter-compression force on the upward-moving piston. At the moment the engine is shut off, this counter-compression force exceeds the piston's upward inertial compression force, forcing the piston downward and causing the crankshaft to reverse. Consequently, the fan or flywheel also reverses direction.

When the fuel injection timing is too late, the formation and combustion of the air-fuel mixture are delayed until the piston descends. Because the combustion space increases rapidly, the required high expansion force cannot be generated. Therefore, at the moment the diesel engine shuts off, the crankshaft's rotational inertia decreases, causing it to stop rotating immediately, manifested as the fan or flywheel stopping abruptly.

Generally, fuel injection pumps in diesel engines that have operated for more than 500 hours or have undergone repair must be adjusted to achieve the optimal fuel injection advance angle (fuel injection timing).