the purpose of the air pump is to supply air to the exhaust
system via the steel "tree" attached to the head, feeding into the exhaust
ports.this gives you excess air so that unburned
gasses can be burned off and converted in the cataytic converter. there is a
check valve in this line which allows air to flow into the ports but does
not allow exhaust to flow back into the pump.the gulp valve on the inlet
side of the engine is opened in deceleration by the increased vacuum in the
manifold allowing air to be pumped into the intake manifold so that there is
ample air to get more complete combustion so that the converter does not
have to work overtime, get red hot and set your mbg on fire when gas leaks
out the bottom of your stromberg carb when the automatic choke screws loosen
up. the air pump does not pump anything out of the cylinders! the rest of
the emmission system is strictly for capturing vapours or gasses that would
normally be discharged into the surrounding air from the crankcase breather,
the carb float chamber or the gas tank.the mgb engine breathes normally by
drawing air thru the anti-run-on valve located in front off the charcoal
canisters.when the ignition is on and the engine is running this valve is
open and air is drawn into the valve cover thru the large inlet tube which
runs to the front radiator valance on the later cars.when you turn the key
to the off position you activate
the aro valve solenoid which closes this valve. the vacuum line which runs
from the manifold to this valve then allows vacuum to flow thru this valve
to th float chamber of the carb which in turn draws down the fuel
level,starves the engine of fuel and shuts it down.after the engine has
stopped turning, the alternator stops producing voltage and you will hear a
distinct click as the aro valve solenoid releases and opens the valve so
that everything is ready for a restart when you turn the key back
on.-----and you all thought the car stopped because you turned off the
ignition-----no! it stopped because you took the fuel away.
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