A cold start is an attempt to start a

vehicle A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), ...

's engine when it is cold, relative to its normal

operating temperature An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...

, often due to normal cold

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmosphere, the ...

. A cold start situation is commonplace, as weather conditions in most climates will naturally be at a lower

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

than the typical operating temperature of an engine.

Causes of cold starts

Cold starts are more difficult than starting a

that has been run recently (typically between 90 minutes and 2 hours). More effort is needed to turn over a cold engine for multiple reasons: * The engine compression is higher as the lack of heat makes

ignition Ignition may refer to: Science and technology * Firelighting, the human act of creating a fire for warmth, cooking and other uses * Combustion, an exothermic chemical reaction between a fuel and an oxidant * Fusion ignition, the point at which a ...

more difficult * Low temperatures cause engine oil to become more

viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the in ...

, making it more difficult to circulate the oil. * Air becomes more dense the cooler it is. This affects the air-fuel ratio, which in turn affects the flammability of the

mixture In chemistry, a mixture is a material made up of two or more different chemical substances which are not chemically bonded. A mixture is the physical combination of two or more substances in which the identities are retained and are mixed in the ...

Solutions to cold starting

The problem of cold starting has been greatly reduced since the introduction of engine starters, which are now commonplace on all modern vehicles. The higher revs that can be achieved using electric starter motors improves the chance of successful

Starting fluid Starting fluid is a volatile, flammable liquid which is used to aid the starting of internal combustion engines, especially during cold weather or in engines that are difficult to start using conventional starting procedures. It is typically avail ...

, a volatile liquid, is sometimes sprayed into the combustion chamber of an engine to assist the starting procedure.

Diesel engines The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-call ...

make use of

glow plug A glowplug (alternatively spelled as glow plug or glow-plug) is a heating device used to aid in starting diesel engines. In cold weather, high-speed diesel engines can be difficult to start because the mass of the cylinder block and cylinder he ...

s to heat the

combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Intern ...

prior to ignition, improving the conditions inside the engine, while certain

manufacturers Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to ...

have incorporated a

block heater A block heater is used in cold climates to warm an engine prior to starting. They are mostly used for car engines; however they have also been used in aircraft engines. The most common design of block heater is an electrical heating element embed ...

, which heats the engine block prior to ignition to reduce the problem of cold starting.

References

Starting systems {{automobile-stub