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Crankshaft Position Sensor
The crankshaft position sensor (Figure 2) provides
the ECU the signals needed to calculate RPM. This
sensor controls the timing for the system to inject
fuel as each intake valve opens, and controls when
to apply voltage to the spark plug for the proper
ignition-timing advance.
Figure 2
Crankshaft Reluctor Wheel
The reluctor wheel (Figure 3) is attached to the back
of the crankshaft accessory drive pulley. This wheel
works with the Crankshaft Position Sensor to
provide a momentary interruption in the magnetic
field, producing the voltage spike used by the ECU
to determine RPM. The large gap in the reluctor
wheel identifies top dead center on the number 1
cylinder. The ECU sequences through the firing
order until the last injector has been opened.
Figure 3
Engine Control Unit (ECU)
The Engine Control Unit (ECU) (Figure 4) collects
information from the intake manifold pressure
sensor, engine RPMs and various other sensors to
determine the amount of compensation needed to
the base injection time.
The ECU ensures the proper amount of fuel and
ignition timing advance is delivered under various
engine loads and RPMs. The fuel injection time is
synchronized to the intake valve opening sequence.
Figure 4
Engine Coolant Temperature Sensor
The coolant temperature sensor (Figure 5) provides
the engine’s current operating temperature to the
ECU. Under cold start conditions, the ECU makes
corrections to the base injection time to keep the
injectors open longer, delivering more fuel during
warm up.
Figure 5
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