MerCruiser 305 CID (5.0L) Service Manual page 479

FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
MOVING DESIRED RPM MODE
IMPORTANT: An improperly adjusted throttle cable can cause the engine idle rpm to
be higher than the normal 600 rpm even when the control lever returns to the idle rpm
position.
A Moving Desired RPM mode has been added to the MEFI 3 ECM. this mode will increase
the desired idle rpm to a calibrated set point according to the throttle position. When the
Throttle Position (TP) sensor is at the closed throttle setting, the ECM will use Idle Air Control
(IAC) and Ignition Control (IC) to maintain the calculated desired rpm. This will smooth the
transition from idle (closed throttle) to higher throttle settings. It will also help maintain
constant low engine speeds from approximately 600 to 1200 rpm. At 5% or greater TP sen-
sor setting, the Moving Desired RPM mode is not active.
Throttle Body Injection Components
FUEL PUMP ELECTRICAL COMPONENTS
When the ignition switch is turned to the RUN position, the ECM will turn ON the fuel pump
relay for two seconds.
When the ignition switch is turned to the crank position, the ECM turns the fuel pump relay
ON causing the fuel pump to start.
If the ECM does not receive ignition reference pulses (engine cranking or running), it shuts
Off the fuel pump relay, causing the fuel pump to stop.
THROTTLE BODY UNIT
The throttle body unit consists of three assemblies.
•
Fuel meter cover and fuel damper
•
Fuel meter body and fuel injectors
•
Throttle Body
Index
Page 5D-26
-Two Throttle Valves To Control Air Flow Into The Engine
-Idle Air Control (IAC) Valve
-Throttle Position (TP) Sensor
SERVICE MANUAL NUMBER 24
90-861327 OCTOBER 1999