Mercury MerCruiser MCM 454 Mag MPI Service Manual page 496

SERVICE MANUAL NUMBER 23
FUEL PRESSURE REGULATOR ASSEMBLY
MEFI 1 and MEFI 2 Only: The pressure regulator is a diaphragm-operated relief valve with
fuel pump pressure on one side, and 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 vacuum drops.
THROTTLE BODY ASSEMBLY
The throttle body assembly is attached to the plenum, and is used to control air flow into the
engine, thereby controlling engine output. 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 also provides the location for mounting the Throttle Position (TP) sensor
for sensing throttle valve position.
Index
90-861326--1 MARCH 1999
Downloaded from https://needmanual.com/
a - Throttle Body
b - Idle Air Control (IAC) Valve
c - Throttle Position Sensor
MULTI-PORT FUEL INJECTION DESCRIPTIONS AND SYSTEM OPERATION
b
c
a
Page 5B-37
71716
72800