ENGINE AND ENGINE SYSTEMS 5540F/YB5515 SERVICE MANUAL
6-14 Published 10-21-2010, Control# 198-04
Control Unit
1. The Electronic Control Unit (ECU) Figure 6-11 is a
simple programmable computer that controls air/fuel
mixtures, spark advance curves and provides electronic
governor control based upon engine and environment
information received from the fuel injection system
sensors. The ECU constantly reads the inputs and
calculates the time the injectors are turned on, tells them
when to turn on, calculates ignition advance and tells the
ignition system when to fire each spark plug.
Sensors
Several sensors are used in the fuel injection system to
provide the ECU with vital operating information.
1. Air Temperature Sensor Figure 6-12
This sensor is used to measure the air temperature in
the intake system. The information obtained is used to
change the air/fuel ratio (mixture) to compensate for
different ambient air temperatures.
2. Coolant Temperature Sensor Figure 6-13
Used to measure the engine coolant temperature, the
ETS provides information for cold or hot correction of the
injection volume and ignition timing. It is also used to
provide gain correction to the governor control during
cold start.
3. MAP Sensor
The Manifold Absolute Pressure (MAP) sensor
Figure 6-14 provides the ECM with a signal proportional
to engine load. This is used in determining injection
volume, acceleration compensation, ignition timing and
governor control.
FIGURE 6-11
p3029
Electronic
Control Unit
FIGURE 6-12
p3032
Air Temperature
Sensor
FIGURE 6-13
p3031
Coolant
Temperature
Sensor
FIGURE 6-14
p3030
MAP Sensor
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