COOLING
90-855347R1 JANUARY 1999 Page 4B-3
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Resistance (k)
Temperature (F)
Temperature Sensor
Temperature Sensor
Two temperature sensors are used to provide cylinder head temperature information to
the ECM. A sensor is mounted in starboard cylinder head and one in the air compressor
cylinder head. The ECM uses this information to increase injector pulse width for cold
starts and to retard timing in the event of an over-heat condition.
An ohms test of the temperature sensor would be as follows:
Insert digital or analog ohmmeter test leads into both TAN/BLACK sensor leads. With en-
gine at temperature (F) indicated, ohm readings should be as indicated ±10%.
NOTE: The air compressor temperature sensor and cylinder head temperature sensors
are the same part number. The ECM has been programmed to activate a warning circuit
at different temperatures depending upon sensor location.
NOTE: The Digital Diagnostic Terminal (DDT) can be used to monitor temperature read-
ings from all three temperature sensors.
2.5 Liter Optimax/DFI Water Flow
Description
Cooling water enters the cooling system through the lower unit water inlets. The pump
assembly forces water through the water tube and exhaust adapter plate passages filling
the power head central water chamber (located behind the exhaust cavity). Water enters
the exhaust cover cavity through 2 holes near the top of the exhaust cover. Water also
exits the top of the exhaust plate through a strainer screen to supply water to the air com-
pressor.
Water exits the exhaust cover cavity through 4 slots (2 each side) filling the water pas-
sages around the cylinders. Water flows around each bank of cylinders to the top of the
cylinder block.
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