Why Can't the Small Gasoline Engine Shut Off?
3 Answers
Small gasoline engine can't shut off because the air piston spring has been compressed for a long time, resulting in shortened length and weakened elasticity. Introduction to small gasoline engines: Refers to reciprocating piston gasoline engines with a wide range of uses other than for vehicles and aviation, with a power of less than 20kW. Most of them are highly versatile and specialized, so they are also called small gasoline engines. General gasoline engines with more than 20kW are mostly modified products of vehicle gasoline engines. Structurally, they can be divided into two-stroke and four-stroke. The power of existing small gasoline engines in China is 0.63-24.00kW; Characteristics of small gasoline engines: The characteristics are small size and light weight, easy to use and operate, and low price. They are mainly used for agricultural and forestry plant protection machinery, garden machinery, small tools, generator sets, construction machinery, fire-fighting series tools, recreational go-karts, water power and aviation model power, etc.
I've worked on many small gasoline engines, and the issue of engines not shutting off is quite common. The most frequent cause is a faulty ignition switch, where the internal contacts may be stuck and won't release, or mechanical components are jammed, keeping the circuit continuously closed. Another key issue is wiring faults, such as short circuits caused by aging or damaged wiring harnesses, allowing current to keep flowing, or when a blown fuse fails to cut off the power source. There's also the case of a malfunctioning generator voltage regulator, where excessively high voltage prevents the engine from stopping. When encountering this situation, I first take safety measures, such as disconnecting the ignition coil power or temporarily blocking the exhaust pipe with a tool to shut down the engine, then systematically check the switch, wiring harness, and voltage regulator. For preventive maintenance, regularly cleaning the switch and inspecting the wiring harness for wear can reduce such failures, ensuring equipment longevity and operational safety.
My lawn mower once had the problem of not being able to shut off, which was extremely frustrating. I found that it's usually caused by the ignition switch button not popping back or the contacts being oxidized. Loose wiring connections can also cause a short circuit, preventing the current from stopping. A blown fuse is a common trigger—just check the fuse box, locate the corresponding position, and replace it. For safety, I immediately cut off the fuel supply or use pliers to clamp the fuel line to avoid sparks causing accidents. If that doesn’t work, call a professional mechanic to check if the relay is stuck. Regular maintenance, like cleaning the switch contacts, can prevent this. Remember not to force it shut, as it can damage more components. Sharing this experience in hopes it helps reduce headaches for others.
