Fuel Metering Flashcards
What are the most common types of fuel metering systems used on small reciprocating engines
Float-type, pressure, and direct fuel injection systems
What function does the mixture control perform
Controls the fuel/air mixture
What generally causes spark plug fouling
an excessively rich mixture at idle
What is the purpose of an accelerating system
It provides an increase in fuel flow in the Venturi to enrich the mixture
What is a carburetor economizer system
provides a richer mixture at high power settings
When the mixture is placed in the idle cutoff position, a slight rise in rpm is noted prior to the engine decelerating. What does this indicate
Idle mixture is set correctly
Why should engine r.p.m be accelerated periodically when making carburetor adjustments
To clear the engine
What maintains the fuel pressure injection carburetor
Engine driven fuel pump
What purpose do turbine engine fuel control units serve
They automatically meter fuel to the engine
What are the two basic types of turbine engine fuel control units
Hydromechanical and electronic
What do turbine engine fuel spray nozzles do
They inject fuel into the combustion area
What are the different engine indications used for trimming a turbine engine
Either EPR or r.p.m is used depending on engine
What type of pump can very the amount of fuel discharged regardless of speed
A variable displacement pump
What is used to keep water, sediment, and foreign matter out of the carburetor
Main fuel strainer
What type of engine driven fuel pump is widely used other than gear or piston pumps
Rotary vane type
What is the purpose of a pressure relief valve in a constant displacement pump
It returns left over fuel that is not used by the engine to the inlet side of the pump
What function do fuel boost pumps perform
Supples pressurized fuel to the fuel pump, which helps prevent vapor lock and cavitation
What is a commonly used type of fuel boost pump
Centrifugal type
Name two categories of turbine engine pumps
Constant and variable displacement
What category is a gear type pump classified in
Constant displacement
When performing an external inspection of an engine driven fuel pump, what should you look for
Leaks and security of mounting
What is the purpose of a shear section of the driveshaft in a dual element constant displacement pump
If one Element seizes it allowing the other element to continue to operate
What is the purpose of a duplex fuel nozzle
Discharges two different spray patterns
What purpose do fuel selector valves serve
Allow tank and engine selection, and provide a means for shutting off fuel flow
What will be the result of using excessively rich idle mixtures
Cause carbon fouling of the spark plug
What position do you place the mixture control of a pressure injection carburetor to stop the engine
Idle cutoff position
What is the typical fuel pressure in a float type carburetor
3-5psi
What are three types of carburetor icing
Throttle, impact, and fuel evaporation icing
What are some of the sources used to heat the fuel in a turbine engine fuel system
Bleed air and engine lubricating oil
