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.
If further technical assistance is needed, our certified car repair technicians
are ready to
answer your car questions.
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