4861 Mercruiser CYLINDER HEAD ASSEMBLY

Electronic Controls
Electronic Control Module
The ECM consists of two main components, the control computer (hardware) and the flash file. The control computer consists of a microprocessor and of electronic circuitry. The flash file contains the engines operational characteristics. The operating maps influence the engines performance.Integrated Sensor Module
The ISM consists of two main components, the control computer (hardware) and the flash file. The control computer consists of a microprocessor and of electronic circuitry. The flash file contains the engines operational characteristics. The operating maps influence the option for gas blending.Engine Governor
The engine ECM governs engine speed. The engine ECM and the flash file work together by controlling the amount of fuel that is delivered by the injectors. Desired engine rpm is determined by the throttle position sensor signal and by certain sensor readings. Actual engine rpm is detected by the engine speed/timing sensor.Fuel Injection
The engine ECM controls the timing and the duration of the fuel that is injected. The engine ECM varies the signals to the fuel injectors. Fuel is injected only while an injector solenoid is energized by a 105 V signal from the engine ECM. The timing of the injection signal determines the engine timing. The length of the injection signal determines engine speed. By controlling the timing and duration of the 105 V signal, the ECM controls the engine speed.Engine Starting and Stopping Procedures
Engine Starting Sequence
1) The generator control module will receive one of the following start signals:
The operator places the control in the RUN mode.
The operator places the control in the AUTO mode and the remote initiate input becomes active.
The operator places the control in the AUTO mode and a start command is sent via the data link.2) The generator control module performs the following system checks:
No system faults are present.
All previous shutdown faults have been reset.
The engine is not already running.
If the prelube (if equipped) is not complete, the generator control module will not crank the engine.3) The generator control module begins the following cranking sequence:
Activate the Starting Motor Relay (SMR).
A start signal is sent to the engine ECM via the Cat Data Link and the fuel control relay is activated.4) The generator control enables cranking the engine until the cycle crank time reaches the setpoint for total crank time or until the engine starts.5) The generator control module deactivates the SMR when the engine speed reaches the setpoint for crank terminate speed.Engine Stopping Procedure
1) The generator control module receives one of the following engine stop signals:
The operator places the control in the STOP mode.
The operator places the control in the AUTO mode and the remote initiate input becomes inactive.
The generator control module begins the cooldown period. Place the generator control in the STOP mode in order to bypass the cooldown . "PRESS ENTER TO BYPASS" and "PRESS ESCAPE TO CONTINUE" will be shown on the display. 2) After the cooldown period, the generator control module sends a shutdown signal to the engine ECM. The engine ECM deactivates the fuel control relay which shuts down the engine.