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How to push start (run start) a car

Push starting (also known as a run start or running start) is a method of starting a vehicle by engaging the manual transmission whilst the vehicle is in motion.  This technique is most commonly used when other starting methods like starting your car with a key or pressing self start doesn't work.  It's mostly caused by a flat battery.

Method to push start a car

The most common way to push start a car is to put the car in first or second gear typically, switching the ignition to on/run, depressing the clutch, and pushing the vehicle until it is at a speed of 5 to 10 mph (8 to 16 km/h) or more, then quickly releasing the clutch to make the engine rotate and fire, then quickly depressing the clutch so it does not stall. This is done by one or two persons pushing the car, pulling or being pushed by another vehicle, and another managing the controls of the car unable to start.  If you're alone, and fortunate to be parked on a hill, you could also use the incline to role down the hill to gain some speed.

Types of vehicles  (Resource:  Wikipedia)

Push starting is most successful when the automobile is using a gasoline engine, uses a carburetor, and uses a capacitor discharge ignition (CDI) or an inductive discharge ignition system. Automobiles with other types of engine, ignition, and fuel delivery configurations may work, but may be more difficult to start. Some engines must have a battery providing some electricity since fuel injection systems must have power to operate.

Automatic or manual gearbox

A vehicle equipped with an automatic transmission (including semi automatic) is difficult to push start since selection of transmission gears is possible only when the internals of such a gearbox are rotating.

Petrol or diesel engines

A diesel engine uses heat and high compression (compression ratios commonly 22:1 versus 9:1 for gasoline) to ignite the fuel. When normally starting a modern diesel engine, it typically uses glowplugs to preheat the cylinder(s). If a battery is completely discharged then it may not provide the necessary electrical power to 'glow' the glowplugs, making the push starting of a diesel vehicle with a dead battery almost impossible.

Fuel delivery systems

Fuel injection is most common for modern gasoline and diesel engines. Fuel injection needs electrical power to open and close the fuel injectors. If a battery is of a sufficiently discharged state that it cannot provide the power to turn an automobile self starter then it may also not be possible to activate the injectors. The most common method to start such a vehicle engine is to jump start it.

A fuel pump is used for fuel injection. It can be mechanically driven or is electrically driven. If electrical then the same problem may arise which the battery cannot turn the pump because it is heavily discharged. A carburettor only needs suction from the internal combustion engine to work best when push starting. Once the engine is running, a fuel pump (mechanical or electrical) will continue to supply fuel to the carburettor.

Ignition systems

A modern gasoline engine contains an electronic ignition system which precisely times the electrical pulse to the spark plug. The advantage of such a device is that it can deliver a full power electrical pulse to the spark plugs even when the alternator is turning very slowly (as in push starting a motor). The out-dated method of a mechanically timed ignition system is that is cannot deliver a full electrical pulse at very low engine revolutions per minute (RPM). This may affect the ease of push starting an engine to life.

Video as demonstration