SERVICE MANUAL NUMBER 23
GENERAL SYSTEM DIAGNOSTICS
Chart A-4 (2 of 5): Fuel System Diagnosis
TEST DESCRIPTION:
2.
Wrap a shop towel around the fuel pressure connector to absorb any small amount of
fuel leakage that may occur when installing the gauge. Ignition “ON,” pump pressure
should be 34-38 psi (234-262 kPa). This pressure is controlled by spring pressure within
the regulator assembly.
NOTE: Fuel pump pressure will read lower if battery is not fully charged.
3.
When engine is idling, high vacuum is applied to the fuel regulator diaphragm. This will
offset the spring and result in a lower fuel pressure. This idle vacuum will vary somewhat
depending on barometric pressure. However, the pressure idling should be less, indicat-
ing pressure regulator control.
6.
Pressure that leaks down is caused by the fuel pressure regulator valve leaking, injec-
tor(s) sticking open, a defective fuel pump or external fuel leak.
11.
Restricting the fuel return line allows the fuel pressure to build above regulated pres-
sure. Pressure should rise to 60 psi (414 kPa) as the fuel return hose is gradually
restricted.
NOTE: Do Not allow the fuel pressure to exceed 60 psi (414 kPa). Fuel pressure in excess
of 60 psi (414 kPa) may damage the Fuel Pressure Regulator.
12.
This test determines if the high fuel pressure is due to a restricted fuel return line or a
pressure regulator problem.
15.
If an injector is stuck open, it will send fuel to its respective cylinder, which may saturate
or foul a spark plug(s). in order to determine which injector(s) is leaking, the spark plugs
must be removed and inspected for fouling or saturation. Once the saturated spark
plug(s) is found, replace the corresponding injector(s) and install new spark plugs.
Index
90-861326--1
MARCH 1999
Page 5E-73
| Categories | Mercury MerCruiser Manuals |
|---|---|
| Tags | Mercury MerCruiser 454 CID, Mercury MerCruiser 502 CID |
| Model Year | 1998, 1999, 2000, 2001 |
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| Document File Type | |
| Copyright | Attribution Non-commercial |
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