Mariner Mercury 105/140 JET, Service Manual

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4B-2 - POWERHEAD 90-824052R3 JUNE 2002
Temperature Sensor
EFI Models – Sensor (in port cylinder head) provides
the ECM signals related to engine temperature to de-
termine the level of fuel enrichment during engine
warm up. The ECM receives information at all engine
temperatures but stops fuel enrichment when engine
temperature reaches 90
°
F (32
°
C). An open circuit
on the temperature sensor will increase fuel flow up
to 40% but will not affect fuel flow at wide open
throttle. If no change occurs when sensor is discon-
nected, sensor may not be functioning properly.
NOTE: TAN/BLUE sensor lead (in port temperature
sensor) provides signal for optional temperature
gauge.
NOTE: If sensor does not make clean contact with
cylinder head, a rich fuel condition may exist.
NOTE: The Digital Diagnostic Terminal (DDT) can be
used to monitor temperature readings from both air
and head temperature sensors.
NOTE: Temperature sensor in starboard cylinder
head on EFI models activates a warning horn when
engine temperature exceeds 240
°
F 8
°
F (115.6
°
C
–13.3
°
C). Warning horn will deactivate when en-
gine temperature drops below 210
°
F 15
°
F (98.9
°
C
–9.4
°
C).
An ohms test of the temperature sensor (in port cylin-
der head) would be as follows:
Insert digital or analog ohmmeter test leads into both
TAN/BLACK sensor leads. With engine at tempera-
ture (F
) indicated, ohm readings should be as indi-
cated
±
10%.
0
15
30
45
60
75
90
105
120
135
150
165
180
195
210
225
240
255
270
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2
Resistance (k )
T
emperature (F
)
Temperature Sensor
Carburetor Models – Temperature sensor in star-
board cylinder head activates a warning horn when
engine temperature exceeds 240
°
F
±
8
°
F (115.6
°
C
±
–13.3
°
C). Warning horn will deactivate when en-
gine temperature drops below 210
°
F
±
15
°
F (98.9
°
C
±
–9.4
°
C).
Temperature sensor in port cylinder head provides
signal for optional temperature gauge.