Mercury 305 CID, Service Manual, Page: 562 / 967

ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY) - 5E-21 90-823225--1 1096
CLEAR FLOOD MODE
If the engine floods, it can be cleared by opening the
throttle half way (50%). (Open throttle handle until re-
sistance from secondary throttle [Multi-Port only] is
felt.) The ECM discontinues fuel injector pulsation as
long as the throttle is between 50 to 75 % and the en-
gine RPM is below 300. If the throttle position be-
comes more than 75% or less than 50%, the ECM re-
turns to the starting mode.
RUN MODE
When the engine is started and RPM is above 300,
the system operates in the run mode. The ECM will
calculate the desired air/fuel ratio based on these
ECM inputs: RPM, Manifold Absolute Pressure
(MAP) sensor, Intake Air Temperature (IAT) sensor
and Engine Coolant Temperature (ECT) sensor.
Higher engine load (from MAP) and colder engine
temperature (from ECT) requires more fuel, or a rich-
er air/fuel ratio.
ACCELERATION MODE
The ECM looks at rapid changes in Throttle Position
(TP) and provides extra fuel by increasing the injector
pulse width.
FUEL CUTOFF MODE
No fuel is delivered by the injectors when the ignition
is OFF, to prevent dieseling. Also, fuel pulses are not
delivered if the ECM receives no distributor reference
pulses, which means the engine is not running. The
fuel cutoff mode is also enabled at high engine RPM,
as an overspeed protection for the engine. When cut-
off is in effect due to high RPM, injection pulses will
resume after engine RPM drops slightly.
POWER REDUCTION MODE
(1996 AND OLDER MODELS)
The ECM will go into power reduction mode when the
following conditions are met:
1. Low oil pressure
2. Engine overheat
3. Low I/O fluid level (MCM)
4. High transmission temperature (MIE)
The ECM recognizes change of state in a discrete
switch input that identifies an abnormal condition that
may affect proper drive train operation.
As an engine protection feature, power reduction
mode allows normal fuel injection up to 2800 RPM.
Above 2800 RPM, fuel delivery is limited to half of the
injectors until RPM lowers to 1200 RPM when normal
fuel injection resumes.
This feature maintains maneuverability of the vessel
while removing the possibility of high RPM operation
until the problem is corrected.
DECELERATION MODE
The IAC is similar to a carburetor dashpot. It provides
additional air when the throttle is rapidly moved to the
idle position to prevent the engine from dying.