Multi-Port Injection Fuel System Diagnosis
Chart A-7 (1 of 6)
SUPPLY LINE
RETURN LINE
ONE PIECE FUEL RAIL ASSEMBLY
72573
CIRCUIT DESCRIPTION:
Ignition ON, pump pressure should be 34-38 PSI
kPa). This pressure is controlled by
spring pressure within the regulator assembly.
(234-262
During engine cranking, the Engine Control Module
(ECM) will turn ON the electric fuel pump in the vapor
separator tank. It will remain ON as long as the en-
gine is cranking or running, and the ECM is receiving
reference pulses. If there are no reference pulses,
the ECM will shut OFF the fuel pump.
3. When the engine is idling, high vacuum is applied
to the fuel regulator diaphragm. This will offset
thespringandresultinalowerfuelpressure.This
idle vacuum will vary somewhat depending on
barometric pressure; however, the fuel pressure
at idle should be less, indicating fuel pressure
regulator control.
The pump will deliver fuel to the fuel rail and injectors,
then to the pressure regulator, where the system
pressure is controlled to about 36 PSI (248 kPa)
nominal. Excess fuel is then returned to the vapor
separator tank.
4. Pressure that leaks down is caused by one of the
following:
•
•
•
Fuel pressure regulator valve leaking.
Injector(s) sticking open.
TEST DESCRIPTION:
Number(s) below refer to circled number(s) on the
diagnostic chart.
Check vent line from VST to see if diaphragm
is leaking.
1.
If pump does not run check fuel pump relay and
fuse.
5.
If an injector is stuck open, it will send fuel to its
respective cylinder, which may saturate or foul
spark plug(s). In order to determine which injec-
tor is leaking, the spark plugs must be removed
and inspected for fouling or saturation. Once the
saturated spark plug(s) is found, replace the cor-
responding injector(s) and install new spark
plug(s).
2.
Wrap a shop towel around the fuel pressure con-
nector to absorb any small amount of fuel leak-
age that may occur when installing the gauge.
Index
5C-60 - ELECTRONIC FUEL INJECTION (MULTI-PORT AND THROTTLE BODY)
90-823224--2 796
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1993, 1994, 1995, 1996, 1997 |
| Download File |
|
| Document File Type | |
| Copyright | Attribution Non-commercial |
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Marine readers have rated 1993 1997 Mercury-MerCruiser GM V8 454 CID 7.4L and 502 CID 8.2L Marine Engines Service Manual Number 16 4.5 out of 5.0 based on 4 product reviews. Hugely helpful service manual! Perfect. Thank you!
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