Henley Street
Shields Road
Newcastle upon Tyne
NE6 2XT
tel: 0191 276

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Injection system components
Air flow meter

Air flow meter

Measures the air flowing
into the engine and sends
the information to the ECU
which calculates the exact
amount of fuel required.
Air mass sensor

Air Mass sensor

This measures the airmass
flowing into the engine and
sends this to the ECU.
The ECU uses this information
to help calculate the required
amount of injected fuel.
Auxiliary air valve

Auxiliary Air Valve

This air valve allows the
engine to receive additional
air during warm up, for optimum
performance and economy.
Canister purge valve

Canister Purge Valve

Fuel vapours that form in
the fuel tank are collected in
a charcoal filter. The canister
purge valve then passes
these gasses into the engine.
Cold start valve

Cold Start Valve

Injects additional fuel into
the intake manifold during
the start up and warm up phase.
Electric fuel pump

Electric Fuel Pump

Ensures a constant supply
of fuel to the engine (It can
be installed directly into
the fuel tank or in the fuel line).
Secondary air pump

Electric Secondary Air Pump

Complying with current emissions
legislation, the secondary air
pump blows fresh air into the
exhaust system after the start up,
ensuring that the CAT reaches
operating temperature quickly
and is not damaged by excess fuel.
Injector

Electromagnetic Injector

This sprays fuel onto the inlet
valve via the inlet manifold,
when electronically triggeredby the ECU.
ECU

Electronic Control Unit (ECU)

50 million pieces of information are
handled every second bythe ECU,
from all the engine sensors.
It determines the quantity of fuel
to suit every condition, controls the injectors, and maintains other components.
In modern systems, it can also
control ignition and diagnose faults.
Idle speed ECU

Electronic Idle Speed ECU

Controls the idle actuator
and maintainsa constant engine
idle speed.
Temperature sensor

Engine Temperature Sensor

This measures the engine
temperature in the coolant
system and sends this
informationto the ECU.
Fuel accumulator

Fuel Accumulator

Ensures the fuel supply system
is kept under pressure after
the engine has been switched off.
This improves the start phase in
specific petrol injection systems.
Fuel filter

Fuel Filter

Removes contamination from the fuel.
Fuel pressure damper

Fuel Line Pressure Dampener

Damps down oscillation
wthin the fuel system.
Fuel rail

Fuel Rail

Feeds fuel at pressure to the injectors.
Fuel pressure regulator

Fuel System Pressure Regulator

Maintains a constant fuel
pressure for fuel that is
supplied to the fuel rail.
Idle actuator

Idle Actuator

Maintains a constant idle speed.
Knock sensor

Knock Sensor

Converts engine combustion vibrations
into electronic signals and sends this
information to the ECU. The ECU then
adjusts the ignition to prevent damage
to the engine.
Lambda sensor

Lambda Sensor

Once the engine has reached operating
temperature this sensor measures
the oxygen content of the exhaust
gas and sends this information to
the ECU which then controls the air/fuel mixture. Lambda sensors should be
replaced according to manufacturers instructions. For some systems there
are sensors at either side of
the catalytic converter.
Mechanical injector

Mechanical Injector

Sprays fuel onto the valves
when a predetermined pressure
is reached. One injector is used for each engine cylinder.
Mixture control Unit

Mixture Controller Unit

Combines the work of the
Air Flow Meter and the Fuel Distributor.
It measures theamount of air flowing into
the engine and determines the
quantity of fuel needed for injection.
Pedal sensor

Pedal Sensor

This records the position of the
accelerator and sends the information
to the ECU asan electronic signal
(as opposed to conventional cables).
The ECU uses this information to control
the air/fuel mixture.
Altitude pressur sensor

Pressure Sensor (Altitude)

Measures the atmospheric
pressure and sends this
information to the ECU as
an electronic signal.
MAP sensor

Pressure Sensor (MAP)

Measures the pressure in the
intake manifoldand sends this
information to the ECU. The ECU
uses this information to control the ignition timing and the air/fuel mixture.
Single point injector

Single Point Injector

This single injector supplies fuel
to all the engine cylinders. It
sprays fuel into the inlet manifold when triggered by the ECU.
Speed sensor

Speed and Reference Mark Sensor

A speed and reference mark
sensor measures the engine speed
and piston position. This information
is sent to the ECU which calculates
the air/fuel mixture and ignition timing.
Thermo switch

Thermo-Time Switch

Limits the amount of additional
fuel injected by the cold start
valve into the intake manifold
during the start up.
Throttle control

Throttle Control Device

Uses information from the ECU to
electronically open and close the
throttle valve.
Throttle valve switch

Throttle-Valve Switch

This measures the position of the
throttle-valve. The information is
sent to the ECU which can alter
air/fuel mixture.
Throttle valve sensor

Throttle-Valve Sensor

Measures the position of the
throttle valve. It sends this
information to the ECU to
adjust the fuel/air mixture.
Throttle body

Throttle-Body Injection Unit

This is used on signal point injection
systems (only one injector). It includes
the injector, fuel pressure regulator,
throttle valve sensors and is known
as a Central Injection Unit.
Vacuum limiter

Vacuum Limiter

Maintains a consistent pressure
difference either side of the
throttle-valve. If the pressure difference
is exceeded, additional air flows
into the inlet manifold.
Warm up regulator

Warm up Regulator

Controls fuel quantity as the engine warms up.

An ever-increasing number of electrical and electro-mechanical components are finding their way into modern cars. Below are some of the components vital to the running of a modern power unit. A small fault in any one of these components can illuminate the dashboard MIL light

The complexity of modern vehicles with their multitude of electronic systems means that the wiring looms joining those components are even more subject to failure.

Multiplexing, where the loom ostensibly can be reduced in size due to the components being voltage controlled from a single wire rather than being individually supplied is, by definition, more sensitive to voltage variation than earlier systems.

Previous poorly repaired accident damage, loose cabling due to a broken securing clip or just old fashioned corrosion can all reduce the voltage in a particular wire causing the component at the end of that wire to fault. Being able quickly to identify, trace and repair the fault makes all the difference.

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