PleasureCraft Engine Group 5.0L, Diagnostic Manual

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5 - 60 Diagnosis 5.0/5.7/6.0/8.1L
MEFI 4 - PCM
M4054P
2-12-04
FUEL
TANK
PRESSURE
REGULATOR
FUEL
FILTER
LOW-
PRESSURE
FUEL
PUMP
FUEL
CONTROL
CELL
FUEL RAIL ASSEMBLY
ENGINE
Fuel Control Cell Fuel System
FUEL
TANK
PRESS.
REG.
FUEL
FILTER
LOW-
PRESSURE
FUEL
PUMP
FUEL
CONTROL
CELL
FUEL RAIL ASSEMBLY
ENGINE
Fuel Control Cell Fuel System
(Returnless Fuel Rail)
Diagnostic Procedure (DP) A-4 Fuel System Diagnosis
•
The fuel pump check valve.
•
The fuel pump fl ex pipe.
•
The valve or valve seat within the fuel pressure
regulator.
•
The fuel injector(s).
4. A fuel system that drops more than 2 psi in 10
minutes after being relieved to 10 psi indicates a
leaking fuel pump check valve.
5. Fuel pressure that drops off during acceleration,
cruise or hard cornering may cause a lean
condition. A lean condition can cause a loss of
power, surging or misfi re.
8. If equipped with vacuum bias fuel pressure
regulator -
When the engine is at idle, the
manifold pressure is low (high vacuum). This low
pressure (high vacuum) is applied to the fuel
pressure regulator diaphragm. The low pressure
(high vacuum) will offset the pressure being applied
to the fuel pressure regulator diaphragm by the
spring inside the fuel pressure regulator. When this
happens, the result is lower fuel pressure. The fuel
pressure at idle will vary slightly as the barometric
pressure changes, but the fuel pressure at idle
should always be less than the fuel pressure noted
in step 2 with the engine OFF.
Circuit Description
When the ignition switch is ON, the ECM activates the
electric fuel pump. The fuel pump remains ON as long
as the ECM receives reference pulses from the ignition
system. If there are no reference pulses, the ECM turns
the fuel pump OFF after about 2 seconds.
The electric pump delivers fuel through an in-pipe fuel
fi lter to the fuel rail assembly. The fuel pump provides
fuel at a pressure above the pressure needed by the fuel
injectors. A fuel pressure regulator, attached to the fuel
rail, keeps the fuel available to the fuel injectors at a
regulated pressure.
Test Description
Number(s) below refer to the step number(s) on the
diagnostic table:
2. When the ignition switch is ON and the fuel pumps
are running, the fuel pressure indicated by the fuel
pressure gauge should read WOT values on the
Master Specifi cations Sheet found at the end of
this section. The spring pressure inside the fuel
pressure regulator controls the fuel pressure.
3. A fuel system that drops more than 2 psi in 10
minutes has a leak in one or more of the following
areas: