Mercury MerCruiser MCM 454 Mag MPI Service Manual page 499

MULTI-PORT FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
FUEL PRESSURE REGULATOR ASSEMBLY
The pressure regulator is a diaphragm-operated relief valve with fuel pump pressure on one
side, regulator spring pressure and intake manifold vacuum on the other. The regulator's
function is to maintain a constant pressure differential across the injectors at all times. The
pressure regulator compensates for engine load by increasing fuel pressure as engine vac-
uum drops.
THROTTLE BODY ASSEMBLY
The throttle body assembly is attached to the plenum. It controls engine output by regulating
the flow of air to the engine. The throttle valves within the throttle body are opened by the
operator through the accelerator controls. During engine idle, the throttle valves are almost
closed, and air flow control is handled by the Idle Air Control (IAC) valve, described below.
THROTTLE POSITION (TP) SENSOR
The throttle body provides the location for mounting the Throttle Position (TP) sensor.
Index
Page 5B-40
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a
a - Throttle Body
b - Idle Air Control (IAC) Valve
c - Throttle Position Sensor
SERVICE MANUAL NUMBER 23
71716
b
c
75723
90-861326--1 MARCH 1999