2-18
IO-240 Series Engine Installation & Operation Manual
31 October 2011
Engine Description
A check valve on the fuel pump permits the use of an auxiliary electric fuel boost pump
during engine priming and starting (allows the aircraft boost pump to bypass the engine
driven fuel pump) or in the unlikely event of an engine driven fuel pump malfunction.
2-2.7.2. Fuel Injectors
The fuel discharge nozzle is located in the cylinder head. The nozzle outlet is screwed into
a tapped fuel nozzle bore in the cylinder head. The nozzle body has a drilled central
passage with a counterbore at each end. The lower end is the fuel outlet. The upper bore
contains a removable jet for nozzle calibration. Near the top, radial holes connect the
upper counterbore with the outside of the nozzle body for air admission. A shroud is
mounted on the nozzle body and extends over the nozzle body. The nozzle shroud is
sealed to the nozzle body by o-rings. The nozzle shrouds are referenced to upper deck
pressure to provide a positive air pressure differential to insure proper fuel atomization at
all operating parameters.
Nozzles are calibrated in several ranges and tuned to each cylinder position for optimum
balance of engine performance and fuel economy. Each nozzle is identified with the
cylinder position number and flow rate engraved on the nozzle body wrench flats.
Figure 2-23. Fuel Injector
2-2.8. Starter Assembly
Several electric starter motors are approved for use on IO-240 engines, all available starter
configurations mount on the rear of the accessory case. Starter engagement is controlled
by the airframe wiring harness and ignition switch contactor.
2-2.9. Alternator
IO-240 engines incorporate a boss on the rear of the engine accessory case for mounting a
direct drive alternator. A 12 volt, 60 amp gear driven alternator is standard equipment for
current engines. Optional belt-driven and lightweight alternators are available, with
retrofit capabilities to older model specifications.
Summary of Contents for IO-240-A
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