Rotax 91 engines: Fuel vaporisation is usually the result of the heat from a
hot
engine, low/nil air flow "boiling" fuel in the fuel line (s) that go from the
mechanical pump to the carburettors.
Boiling/vaporization of the fuel in these lines, is most likely to occur when a
hot engine is shut down. No air & fuel flow.
Keeping fuel running through these lines will allow "cooling" to take place.
Rotax have come up with a partial "fix". It is restricted "bleed" system where
fuel vapour and fuel can be vented back to the tank. This allows fresh cool fuel
to charge the system close to the carburettors (there can still be a brief
period of rough running as the hot gaseous fuel is passes through the
carburettors
giving a sub optimal fuel/air mix).
Using your auxiliary fuel pump on the ground, to push the hot fuel/gas back to
the tank and replace it with fresh cool fuel, may certainly assist in speeding
the recovery from the fuel vaporisation state.
Using your auxiliary pump continuously will add nothing to your engines
performance
but is likely to drain your wallet a but quicker.
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