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SSeeccttiioonn 77
DDIIAAGGNNOOSSTTIICC TTEESSTTSS
TEST 39 - CHECK OIL PRESSURE SWITCH
DISCUSSION:
Also see “Operational Analysis” on Pages 18-23. The
Low Oil Pressure Switch is normally-closed, but is
held open by engine oil pressure during cranking and
startup. Should oil pressure drop below a safe level,
the switch contacts will close to ground the Wire 85
circuit. Engine controller board action will then initiate
an automatic shutdown.
If the switch fails CLOSED, the engine will crank and
start, but will then shut down after a few seconds.
If the switch fails OPEN, low oil pressure will not
result in automatic shutdown.
Figure 7-46. – Oil Pressure Switch
PROCEDURE:
1. Check engine oil level. If necessary, replenish oil level to the
dipstick “FULL” mark.
2. Set a VOM to its “Rx1” scale and zero the meter.
3. Connect the meter test leads across the switch terminals, with
engine shut down. The meter should read
“
Continuity”. A small
amount of resistance is acceptable.
4. Crank the engine. Oil pressure should open the switch contacts
at some point while cranking and starting. Meter should then
indicate “Infinity”.
5. If the contacts did not open in Step 5, remove the low oil pres-
sure switch and connect an oil pressure gauge in it’s place.
Start the engine and measure oil pressure. Pressure should be
above 10 psi.
RESULTS:
1. In Step 3, if “Continuity” is not indicated, replace the switch.
2. If oil pressure checked good in Step 5, but Step 4 measured
“Infinity,” replace the low oil pressure switch.
3. If oil pressure is below 10 psi, determine cause of low oil pres-
sure. Refer to Engine Service manual No. 0E2081 for further
engine service information. Verify that the oil is the proper vis-
cosity for the climate and season.
4. If all steps check GOOD, go to Test 40.
TEST 40 - TEST OIL TEMPERATURE SWITCH
DISCUSSION:
If the engine cranks, starts and then shuts down, one
possible cause of the problem may be a high oil tem-
perature condition. Protective shutdown is a normal
occurrence if the oil temperature switch exceeds
approximately 270°F for gasoline units, or 284°F for
LP units.
Figure 7-47. – Oil Temperature Switch
PROCEDURE:
1. Remove Wire 85 from Oil Temperature Switch terminal and
start the generator. If engine starts and runs now, but shuts
down when Wire 85 is connected to the switch terminal, the fol-
lowing possibilities exist:
a.Oil temperature is too high.
b.The oil temperature switch has failed closed or
is shorted to ground.
2. Remove the switch and place its sensing tip into oil (Figure 7-
48). Place a thermometer into the oil.
3. Connect the test leads of a VOM across the switch terminals.
The meter should read “Infinity”.
4. Heat the oil. When oil temperature reaches approximately 270-
284°F., the switch contacts should close and the meter should
read “Continuity”.
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