Forklifts are classified as vehicles with small engines, the same category wherein lawnmowers are classed. Forklift engines all follow the principles of internal combustion. Different lift truck models and brand names would have varying engine design and layout. Forklifts are designed more toward producing high torque than for speed. They generally are geared to low speeds. The engine runs the drive wheels of the forklift. The engine is also needed to lower and lift the forks via a series of chain pulleys. The majority of forklift engines which are modern are fueled by propane since they would be utilized indoors, where diesel and gasoline engines would be inappropriate because of the exhaust they produce.
Normally, the lift truck is a four-cylinder engine-block. The engines of the forklift are like car engines as they hold pistons connecting to a camshaft. The head of each cylinder consists of an intake hatch, an exhaust hatch and a spark plug, each of them spring-loaded and one-way.
When the driver starts up the engine of the forklift, propane passes through the opened throttle-plate in a fine spray and mixes together with air which comes from the mass air intake before moving into the cylinder head intake hatches. Each one of the four pistons is staggered to rise in an exact sequence, compressing the air and propane mixture as each piston rises to the top of the head. With very precise timing, the battery and alternator of the engine generate an electrical current which passes through the spark plug. The fuel ignites leading to an explosion which drives the piston back down to the bottom of the cylinder, leading to a continuous turning of the camshaft. An air pressure imbalance in the cylinder causes the exhaust to be drawn out through the exhaust hatch when more fuel passes into the cylinder. Propane burns a lot cleaner than diesel and gasoline and the exhaust is not as harmful.