Fuel Pumps
High-wing aircraft use gravity as the
backup fuel pressure source to the
mechanical engine pump, but low-wing designs require an additional
boost pump. Be sure to conduct regular
inspections of the boost pump filter to
detect excessive wear materials before
the pump fails. The only real difference
between the “aircraft quality” facet fuel
pumps and the “automotive quality”
one is the testing done at the end of
the production and parts manufacturer
approval process. They don’t last any
longer, and you should plan on proactive replacement at some point.
Mechanical fuel pumps generally use
a diaphragm design and have an overflow tube that can be used to detect
failures of the rubber diaphragm. If you
see fuel dripping from the tube, replace
the pump before further flight.
collected at the bottom. This is especially true if you use auto fuel, which
has a much shorter shelf life.
With thorough inspections and
regular maintenance, you may never
experience an in-flight fuel system failure. Keeping the tanks full, on the
other hand, is up to you on each preflight. Fuel may seem expensive when
you’re at the pump, but it always seems
cheaper when you’re airborne without
enough on board!
Jeff Simon is president of Approach
Aviation, a provider of educational
products, tools, and supplies for aircraft
owners. To learn more about aircraft
ownership and maintenance, visit
www.ApproachAviation.com or call
877-564-4457.
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Priming Systems
Priming systems require regular maintenance at both ends of the system. If you
have a manual primer pump, you know
that it gets stiff over time. The fix is
simple: Unscrew the collar and pull the
plunger out of the pump (use a rag to
collect the excess fuel or drain the tanks
as necessary), clean the plunger, install
new O-rings, and lube the O-rings with
a special fuel-resistant lubricant (usually
the same lube used for the fuel valves).
At the other end of the system,
primer nozzles get clogged easily but
can be kept in good condition by regular removal and cleaning with Hoppe’s
Gun Cleaner Solvent.
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Carburetors and
Fuel-Injection Systems
The final part of the fuel system is
the carburetor or fuel-injection sys-
tem, depending on the engine design.
Maintaining carburetors and injection
systems is a complex subject. But, suf-
fice it to say, it’s critical to ensure that
all screens and injectors are cleaned
on a regular basis. If your engine has a
carburetor, it’s imperative that you also
drain the carburetor bowl to eliminate
contaminants and water that may have
