Mechanics

Emissions Air Pump

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AIR Pump (Smog Pump)
AIR Pump (Smog Pump)

Air injection pumps or "smog pumps" as they are commonly called, are emissions devices used to clean up and aid in the burning of emissions such as carbon monoxide and hydrocarbons. These pumps inject clean air into the exhaust system to aid the catalytic converter in burning the excess emissions created at certain times of a vehicles operation. Automotive manufacturers began using these pumps in the late 60's, but by the mid 70's almost all vehicles had them as standard emissions equipment.

Air pump systems consist of a few basic parts, depending on how old the vehicle is. The first Air systems were just a serpentine belt driven pump, hoses, check valves at the exhaust manifolds, and a vacuum operated valve that directed air flow from the pump depending on throttle position. As emissions systems became more complex, so did the Air system. Manufacturers began using temperature control switches to dictate when the control vacuum could work the valves, electric solenoids were incorporated as well. Oxygen sensors can tell when the Air system is needed and whether or not it is working properly, causing a check engine light to appear. Newer vehicles use an electric motor instead of a belt driven pump that is controlled via the computer PCM. This allows the PCM to use the information gathered from the monitoring sensors to know when the Air pump needs to be turned on, and also eliminates drag on the engine, which is creating free power.

As vehicles became more advanced and cleaner burning, use of the Air pump has faded. There are still a few vehicles that use them today, but it is mostly trucks, where higher horsepower is needed, thus they aren't as clean burning and require a little extra help meeting emissions standards. The pumps don't run constantly, but mostly at cold start up when the system is in "Open Loop", which means it is using set parameters rather than live information to run the vehicle, as a rich condition is required for a cold start, or when heavy throttle is being used and emissions are at a high level.

There isn't much maintenance required for these pumps. If your vehicle has a belt driven pump, be sure the belt is in good condition and properly tensioned. When Air pumps fail it can cause backfiring in the exhaust system, so be sure all emissions related equipment is in proper working order. Air pumps also tend to accumulate moisture inside the pump body, this can cause the veins to stick and create a scraping or grinding style noise. If your pump is doing this, you may want to consider replacing it before it causes more problems. Always use high quality OEM (Original Equipment Manufacturer) replacement parts or the equivalent. Replacing most Air pumps isn't much more complicated than replacing an alternator, the basic tools are needed (socket set, wrenches), and be sure to use the exact replacement part for your vehicle.

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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-08-16)