PleasureCraft Engine Group 5.0L, Diagnostic Manual

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3A - 4 Fuel Metering System 5.0/5.7L
MEFI 4 - PCM
Figure 3-3 - Fuel Rail Assembly
Figure 3-4 - Fuel Injector Assembly (Typical)
9P 0413-SY
1 SOLENOID ASSEMBLY
2 SPACER AND GUIDE
ASSEMBLY
3 CORE SEAT
4 BALL VALVE
5 SPRAY TIP
6 DIRECTOR PLATE
7 SPRAY HOUSING
8 CORE SPRING
9 SOLENOID HOUSING
10 SOLENOID
11 FUEL INLET FILTER
11
10
9
8
7
6
5
4
3
2
1
4-11-96
Fuel Injectors
The fuel injector assembly is a solenoid-operated device,
controlled by the ECM, that meters pressurized fuel to a
single engine cylinder (Figure 3-4). The ECM energizes
the injector solenoid, which opens a ball valve, allowing
fuel to fl ow past the ball valve, and through a recessed
fl ow director plate. The director plate has six machined
holes that control the fuel fl ow, generating a conical spray
pattern of fi nely atomized fuel at the injector tip. Fuel is
directed at the intake valve, causing it to become further
atomized and vaporized before entering the combustion
chamber.
An injector that is stuck partly open would cause loss
of pressure after engine shut down. Consequently, long
cranking times would be noticed. Dieseling could also
occur, because some fuel could be delivered to the engine
after the ignition is turned “OFF.” A fuel injector that does
not open, may cause a “no-start” or a misfi re.
Fuel Pump Electrical Circuit
When the ignition switch is turned “ON,” the ECM turns
the fuel pump relay “ON” for two seconds causing the fuel
pump(s) to pressurize the MEFI fuel system.
When the ignition switch is turned to the crank position,
the ECM turns the fuel pump relay “ON” causing the fuel
pump to run.
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.
An inoperative fuel pump relay will result in an “Engine
Cranks But Will Not Run” condition.
Fuel Rail Assembly
The fuel rail (Figure 3-3) is mounted to the engine intake
manifold, and performs several functions. It positions the
injectors in the intake manifold, distributes fuel evenly to
the injectors, and integrates the fuel pressure regulator
into the fuel metering system.