Mariner Mercury 105/140 JET, Service Manual

Page: 218 / 797

90-824052R3 JUNE 2002 FUEL SYSTEMS - 3C-11
EFI System Tests
•
EFI Electrical System and ECM Check
•
Fuel Gauge Connection/Pressure Test
•
Vapor Separator Fuel Delivery Test
•
Vapor Separator Float Test
•
Water Separating Filter Flow Test
•
Pulse Fuel Pump Delivery Test
•
Final Filter Check
•
Fuel Pressure Regulator Test
•
Electric Fuel Pump Test
•
Injector Electrical Test
•
Injector Fuel Delivery Test
•
Injector Operating Test (Manifold Cover
Removed)
•
Induction Manifold Leak Check (Manifold Cover
Removed)
•
Sensor Tests
Safety Precautions
CAUTION
Always use approved safety glasses or goggles
when working on pressurized fuel systems.
DANGER
Outboard motor fuels are extremely flammable.
Do not show open sparks or flames when work-
ing near fuel systems.
WARNING
To avoid potential fire hazards, use extreme cau-
tion when connecting and disconnecting fuel
line connections and test adaptors. Do not allow
fuel to spill on hot engine parts or on live electri-
cal connections.
CAUTION
Wipe up fuel spills immediately.
CAUTION
Depressurize fuel system prior to opening line
connections or removing fuel system
components.
DANGER
Perform the tests in this section in a well
ventilated area to avoid being overcome by fuel
vapors or poisonous exhaust gases.
WARNING
Disable the ignition system by grounding
mercury switch prior to performing any tests that
require removal of the induction manifold cover.
Fuel Injection System Function
Fuel is delivered directly to the engine by way of fuel
injectors. These injectors are provided with a
constant
supply of fuel (36 to 39 psi; 248 to 269 kPa)
delivered to the fuel rail. The injectors are opened
and closed electronically by the Electronic Control
Module (ECM). The ECM receives input signals from
various sensors in the EFI system which in turn
transmits controlling outputs (open/close) to the
injectors. The length of time the injectors stay open
is considered pulse width. The pulse width will widen
(richer) or narrow (leaner) depending on signals
ECM receives from sensors, to allow efficient
operation at all speeds and conditions.
IMPORTANT: The following preliminary steps
MUST BE FOLLOWED before attempting EFI
problem diagnosis.