Manifold Absolute Pressure (Map) Sensor; Air Temperature Sensor; Direct Injectors; Fuel Injectors - Mercury Optimax 115 Service Manual

Manifold Absolute Pressure (MAP) Sensor

The MAP sensor is mounted between the cylinder heads. A vacuum hose connects the
map sensor to the intake manifold. The ECM regulates fuel flow, in part, based on man-
ifold absolute pressure. Drawing a vacuum on the MAP sensor hose will create a lean fuel
condition.

Air Temperature Sensor

The air temperature sensor is mounted on the intake manifold. The ECM regulates fuel
flow, in part, based on manifold air temperature. As air temperature increases, the ECM
decreases fuel flow.

Direct Injectors

6 direct injectors (1 per cylinder) are used to inject a fuel/air mix into cylinders. Injectors
are mounted between fuel rails and cylinder heads.
Connect meter leads between each in-
jector terminal pin.

Fuel Injectors

6 fuel injectors (1 per cylinder) are used to provide fuel from the fuel rail to the direct injec-
tors. The fuel injectors are mounted in the fuel rail.
Connect meter leads between each in-
jector terminal pin.

Disconnecting Harness Connectors from Ignition Coils and/or Injectors

a -

Troubleshooting

The ECM is designed such that if a sensor fails, the ECM will compensate so that the en-
gine does not go into an over-rich condition.
Disconnecting a sensor for troubleshooting purposes may have no noticeable effect.
90-855347R1 JANUARY 1999
Direct Injector Ohm Test
Fuel Injector Ohm Test
a
Wire Clip (push center down to remove)
(Injector Lead Disconnected)
1 - 1.6 W
(Injector Lead Disconnected)
1.7 - 1.9 W
54871
IGNITION
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