Mercury 305 CID, Service Manual, Page: 566 / 967

ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY) - 5E-25 90-823225--1 1096
FUEL INJECTORS
The EFI injector assembly is a solenoid-operated de-
vice, controlled by the ECM, that meters pressurized
fuel to a single engine cylinder. The ECM grounds the
injector solenoid, which opens a pintle valve, allow-
ing fuel to flow past the pintle valve. The injector tip
has holes that control the fuel flow, generating a coni-
cal spray pattern of finely atomized fuel at the injector
tip. Fuel is directed at the intake valve, causing it to
become further atomized and vaporized before en-
tering the combustion chamber.
An injector that is stuck partly open will cause loss of
pressure after engine shutdown. This can result in
long cranking times. Dieseling can also occur, be-
cause some fuel might be delivered to the engine af-
ter the ignition is turned OFF.
72970
c
a
b
s
r
o
n
m
J
g
d
e
f
h
i
k
l
p
q
a - Needle Valve
b - Nozzle
c - Cap
d - O-Ring
e - Valve Stopper
f - Core
g - O-Ring
h - Spring
i - Housing
j - Solenoid Coil
k - Tape
l - Bobbin
m - O-Ring
n - Inner Collar
o - Sleeve
p - Terminal
q - Connector
r - Filter
s - O-Ring
PRESSURE REGULATOR ASSEMBLY
The pressure regulator is a diaphragm-operated re-
lief valve with fuel pump pressure on one side, and
regulator spring pressure and intake manifold vacu-
um on the other. The regulator’s function is to main-
tain a constant pressure differential across the injec-
tors at all times. The pressure regulator
compensates for engine load by increasing fuel pres-
sure as engine vacuum drops.
71716
Throttle Body Assembly
The throttle body assembly is attached to the ple-
num, 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.
The throttle body also provides the location for
mounting the Throttle Position (TP) sensor for sens-
ing throttle valve position.
72800
b
c
a
a - Throttle Body
b - Idle Air Control (IAC) Valve
c - Throttle Position Sensor