Push start
Encyclopedia
Push starting, also known as bump starting, pop starting or crash starting is a method of starting a motor vehicle
with an internal combustion engine
by engaging the manual transmission
through the motion of the vehicle. The technique is most commonly employed when other starting methods (automobile self starter
, kick start
, etc) are unavailable.
The most common way to push start a car is to put the transmission in second gear, switching the ignition on, applying the clutch, and pushing the car until it is at a speed of around 5 to 10 mph (8 to 16.1 km/h). This can be done by one person on a motorcycle, or with a car or truck if they are strong enough and/or the car is light enough and/or the vehicle is facing down a hill; a heavier vehicle requires help if not on a hill. When at speed, the clutch is quickly released. By pushing the car, the wheels make the gearbox rotate, and by engaging the gear with the clutch, contact is made between the wheels and the engine, which may make the engine start by the power of the turning wheels (as the engine's starter would normally do). As soon as the engine can be felt and heard starting, it is advisable to again press in the clutch to prevent the engine stalling, or the vehicle jerking out of control. A too slow rolling speed may result in the engine not being able to start.
If the vehicle's battery is severely discharged, the push starting technique can be unsuccessful, as the battery may not be able to provide sufficient voltage for the ignition system to function (or in the case of a diesel engine
, to preheat the glow plugs, although this will not generally prevent starting altogether but just make it much more difficult). Also vehicles with an electronic engine management system will not start if the battery does not provide sufficient voltage to operate it. In such cases, recharging the battery or attempting a jump start
is a better option.
Push starting a car is typically only possible in manual transmission
vehicles, as automatic transmissions usually depend on pressure generated from a pump driven off the input side of the transmission to operate the gear selection mechanism. With the engine not running, this pump is inoperative, so the transmission remains in neutral and cannot transmit drive to the engine. Even if this was not the case the poor performance of the torque converter at transmitting torque in the reverse direction would require the vehicle to be moving at an unreasonably high speed for the technique to work. Most vehicles with automatic transmission
s cannot be started this way because the hydraulic torque converter
in the transmission will not allow the engine to be driven by the wheels (some very old automatic transmissions, e.g., General Motors' two-speed Powerglide transmission, have an extra pump on the output shaft which can power the transmission's hydraulics, and cars equipped with such transmissions can be push started).
In the early 20th Century, many motorcycles could only be push started; the 1908 Scott
was distinguished by introducing a kick start
er feature. Excelsior Motor Company
's Welbike
, intended to be carried by paratroopers in World War II, was designed to be started only by push starting.
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...
with an internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
by engaging the manual transmission
Manual transmission
A manual transmission, also known as a manual gearbox or standard transmission is a type of transmission used in motor vehicle applications...
through the motion of the vehicle. The technique is most commonly employed when other starting methods (automobile self starter
Automobile self starter
A starter motor is an electric motor for rotating an internal-combustion engine so as to initiate the engine's operation under its own power.- History :...
, kick start
Kick start
Kick start refers to a method of starting an internal combustion engine by pushing a ratcheting lever with one's foot. Kick start mechanisms were almost universally a part of motorcycle engines before the mid-1970s, and were phased out of production over the next twenty years or so as electric...
, etc) are unavailable.
The most common way to push start a car is to put the transmission in second gear, switching the ignition on, applying the clutch, and pushing the car until it is at a speed of around 5 to 10 mph (8 to 16.1 km/h). This can be done by one person on a motorcycle, or with a car or truck if they are strong enough and/or the car is light enough and/or the vehicle is facing down a hill; a heavier vehicle requires help if not on a hill. When at speed, the clutch is quickly released. By pushing the car, the wheels make the gearbox rotate, and by engaging the gear with the clutch, contact is made between the wheels and the engine, which may make the engine start by the power of the turning wheels (as the engine's starter would normally do). As soon as the engine can be felt and heard starting, it is advisable to again press in the clutch to prevent the engine stalling, or the vehicle jerking out of control. A too slow rolling speed may result in the engine not being able to start.
If the vehicle's battery is severely discharged, the push starting technique can be unsuccessful, as the battery may not be able to provide sufficient voltage for the ignition system to function (or in the case of a diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
, to preheat the glow plugs, although this will not generally prevent starting altogether but just make it much more difficult). Also vehicles with an electronic engine management system will not start if the battery does not provide sufficient voltage to operate it. In such cases, recharging the battery or attempting a jump start
Jump start (vehicle)
A jump start, also called a boost, is a method of starting an automobile or other vehicle powered by an internal combustion engine when the vehicle's battery has been discharged. A second battery is temporarily connected to provide starting power to the disabled vehicle...
is a better option.
Push starting a car is typically only possible in manual transmission
Manual transmission
A manual transmission, also known as a manual gearbox or standard transmission is a type of transmission used in motor vehicle applications...
vehicles, as automatic transmissions usually depend on pressure generated from a pump driven off the input side of the transmission to operate the gear selection mechanism. With the engine not running, this pump is inoperative, so the transmission remains in neutral and cannot transmit drive to the engine. Even if this was not the case the poor performance of the torque converter at transmitting torque in the reverse direction would require the vehicle to be moving at an unreasonably high speed for the technique to work. Most vehicles with automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...
s cannot be started this way because the hydraulic torque converter
Torque converter
In modern usage, a torque converter is generally a type of hydrodynamic fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load...
in the transmission will not allow the engine to be driven by the wheels (some very old automatic transmissions, e.g., General Motors' two-speed Powerglide transmission, have an extra pump on the output shaft which can power the transmission's hydraulics, and cars equipped with such transmissions can be push started).
In the early 20th Century, many motorcycles could only be push started; the 1908 Scott
The Scott Motorcycle Company
The Scott Motorcycle Company was owned by Scott Motors Limited, Shipley, West Yorkshire, England and was a well known producer of motorcycles and light engines for industry...
was distinguished by introducing a kick start
Kick start
Kick start refers to a method of starting an internal combustion engine by pushing a ratcheting lever with one's foot. Kick start mechanisms were almost universally a part of motorcycle engines before the mid-1970s, and were phased out of production over the next twenty years or so as electric...
er feature. Excelsior Motor Company
Excelsior Motor Company
Excelsior, based in Coventry, was a British bicycle, motorcycle and car maker. They were Britain’s first motorcycle manufacturer, starting production of their own ‘motor-bicycle’ in 1896...
's Welbike
Welbike
The Welbike was a British single-seat motorcycle devised during World War Two at Station IX — the "Inter Services Research Bureau" — based at Welwyn, UK, for use by Special Operations Executive . It has the distinction of being the smallest motorcycle ever used by the British Armed Forces,...
, intended to be carried by paratroopers in World War II, was designed to be started only by push starting.