Parting Thoughts

A Short Primer on Marine Gas Engine Control Computers

By Robert Van Brunt, Chief Petty Officer U.S.G.G. ret

The Electronic Control Unit (ECU) or Electronic Control Module (ECM) (In this article we are using Volvo terminology, but all manufacturers now have similar control.) controls the fuel air mixture and spark advance or retard. It also stores data from the engine sensors. This data can be retrieved from the ECM using the DLC connector (the automobile DLC has 12 pins; the marine DLC has 10 pins). The technician attaches a scan or code tool to the DLC and can determine the operation of all the controlling sensors.

The automotive ECU has an exhaust oxygen sensor which maintains a fuel air mixture of 14.7:1 at full load, so that the catalytic converter will operate at full efficiency. Automobiles also have an AC on/off sensor and a MPH sensor. None of these however are used on the Volvo Penta Marine Engine system.

The Volvo Penta ECM has the following sensors to control engine operation.

MAP: Manifold Absolute Air Pressure, measures engine load and controls fuel mixture & spark advance.

ETC: Engine Coolant Temp, measures engine coolant temperature and controls fuel mixture, spark advance and idle speed.

TP: Throttle Position Sensor, measures throttle position to control acceleration & idle speed.

KS: Knock Sensor, detects detonation in the combustion. This input will make the ECM enrich the fuel air mixture by 7% and retard spark timing to the maxim of 10% to stop the detonation.

RPM: Engine Revolutions per Minute: input from the Ignition Control Module.

Categories: The Express

Tags: ECM, Electronic Control Module, Electronic Control Unit, fuel air mixture, fuel mixture, spark advance

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