Reply for Griffo:
For information I'm in the UK.
I agree that having the fuel pump on will not prevent vapour lock, but having
positive
pressure in the fuel system will help reduce the chance of it as any vapour
in the fuel line will be pushed through the fuel lines back to the tank.
I also believe that it helps starting especially when the engine is hot and the
risk of vapour lock is greater.
On the Vans RV12, the fuel pump comes on with the master switch, there is no
separate
switch to turn off the pump, the only way to turn it of is to pull the
circuit breaker/fuse If you search on the Vans forums, you will learn that one
reason for having the pump on all the time is to help prevent vapour lock. Vans
consider the pump an expendable item as it's cheap to replace.
The downside to leaving it on all the time is that (without a fuel pressure
gauge
as in my aircraft) you will not know if the mechanical pump has failed. This
is why I occasionally turn off the electric pump at a safe altitude to see if
the low fuel pressure light comes on which will indicate a problem with the
mechanical pump.
I'm interested to learn if anyone has a valid reason for not leaving the
electric
pump on all the time.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=501697#501697
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