Working of Continuous Injection System (CIS) in an Automobile
                     Working of Continuous Injection System (CIS) in an Automobile
Gary Martin
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Gasoline engine automobiles use both mechanical and electronic 
fuel injection systems. Diesel engines are mostly equipped with 
mechanical type injection systems. Due to advancement in 
technology, mechanical injection system were replaced by 
electronic fuel injection in diesel engines. We are going to discuss 
the working of continuous Injection system.
Water pump replacement Working of continuous injection 
system (CIS)
The Continuous Injection System (CIS) is a mechanical fuel 
injection system. The basic working principle of CIS is 
continuously injection of fuel into the intake valve of the engine 
through the electric pump. The measure of fuel supplied is 
measured by an air flow measuring device. Some CIS systems 
are equipped with feedback controllers.
•The primary fuel circuit comprises an electric pump used to suck 
the fuel from fuel tank. The fuel then enters an accumulator. The 
accumulator is a container that is located in the fuel line. It 
consists of a spring-loaded diaphragm. The diaphragm performs 
fuel damping and delays the pressure build-up initially when you 
start the engine.
•When you shut down the engine, the expanded chamber (in the 
accumulator) will keep the system under required pressure for a 
good hot restart with no vapor locking – a problem generally 
associated with gasoline engines. Fuel is supplied through a large 
fuel filter to mixture control unit.
•The mixture control unit is an important component of the CIS 
system. It consists of an airflow sensor and a fuel distributor. The 
air sensor connects a counterbalancing lever.
•The air sensor and lever are freely suspended bodies that move 
up and down on a fulcrum connected to the lever. The accelerator 
pedal link is connected to a throttle that is closer to the manifold 
and intake valves of an air sensor. By pressing the accelerator 
pedal, the throttle valve opens.
•In order to maintain accurate fuel pressure, a pressure regulator 
or a pressure relief valve is located in the primary fuel circuit of the 
fuel distributor and the excess fuel is sent back to the fuel tank via 
a return line. An appropriate pressure difference has to be 
maintained and it’s controlled by a pressure valve.
The valve consists of a spring loaded diaphragm of steel and an 
outlet to the fuel injectors. The diaphragm keep lower chambers 
and the upper chambers away from each other. The valves keeps 
the exact pressure difference. The diaphragm opens to the extent 
depending on the measure of fuel flows.
The diaphragm opens less if a lower amount of fuel goes into the 
upper chamber, and less fuel goes to the injectors. A consistently 
maintained difference in pressure in the upper and lower 
chambers.
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