> I was originally told that the 914 pumps had check valves in them. Upon
> obtaining them and investigating by pumping gasoline from one backwards
> into the other this was found not to be the case. So make sure you account
> for this and install some check valves.
I noted that too but did not test how much pressure loss results. The
Rotax 914 manual states check valves aren't necessary. The pump mfr
states they are needed where the rather high pressures of which the pump
is capable are required. But Rotax also says they have no liability if
this pump is not used.
This is not to suggest that one cannot find two check valves to be
trusted to not fail in unison, but I am concerned about this: If a
regulator failure, or return line blockage, should occur, there will be
engine problems. The nipple fitting at the front of the pump seems
clearly less secure than at the supplied T-fitting, or at the engine.
Going to full pressure, that one could pop. While attention is focused
on engine malfunction, fuel will be pumped inside the fuselage at a rate
of about a gallon per minute!
In one auto application I know well, an older fuel-injected design of
only 20psi, clamped nipple fittings are not used. In auto recalls, this
is one of them problem areas where they sometimes get it wrong as hoses
age and/or they use lousy hose fittings. I wonder if both Rotax and
Europa could be in error. Maybe Rotax knows the pump leaks back a bit,
the 914 manual is a poor translation, and the overall design is to
prevent potential excess pressure on hose fittings they shouldn't really
be using?
Regards,
Fred F.
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