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Fuel System
General
This chapter describes the fuel injection system
installed on the TSI0L-550-C and provides
scheduled maintenance information.
WARNING
The use of fuel with an octane rating lower than
specified can result in destruction of an engine
the first time high power is applied. This would
most likely occur on takeoff. If the aircraft is
inadvertently serviced with the wrong grade of
fuel, then the fuel must be completely drained
and the tank properly serviced.
Fuel System Description
The fuel injection system is of the multi-nozzle,
continuous-flow type which controls fuel flow to
match engine requirements. Any change in air
throttle position, engine speed, deck pressure, or a
combination of these, causes changes in fuel
pressure in the correct relation to engine
requirements.
The fuel pump is a single stage, vane-type pump. It
is driven directly by the engine and its flow rate
depends on engine RPM. An aneroid unit is
incorporated as an integral part of the pump and
functions to increase pump output during high
manifold pressure operation. The fuel pump
delivers liquid fuel to the fuel metering unit.
9-2
The fuel metering unit/air throttle controls the
amount of intake air admitted into the intake
manifold and meters the proportionate amount of
fuel to the fuel manifold valve.
The manifold valve receives fuel from the metering
unit. When fuel pressure reaches approximately 3.5
psi, the valve in the manifold valve admits fuel to
the six ports in the manifold valve (one port for
each nozzle line). The manifold valve also serves
to provide a clean cutoff of fuel to the cylinder
when the engine is shut down.
The injector nozzle lines connect the manifold
valve to the six fuel injector nozzles.
The injector nozzles (one per cylinder) are "air
bleed" type fuel nozzles which direct fuel directly
into the intake port of the cylinder. When the
engine is running, flow through the nozzle is
continuous and will enter the cylinder combustion
chamber when the intake valve opens.
Since the size of the fuel nozzle jets are fixed, the
amount of fuel flowing through them is determined
by the pressure drop across the jet. For this reason,
fuel flow may be accurately determined by
measuring the pressure at the manifold valve, and
deck pressure fed to the nozzle "air bleed"
chamber (deck pressure).
All of the items described are interdependent on
each other to meter the correct amount of fuel
according to the power being developed by the
engine.
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