Lubrication System; Testing The Oil Pump - MTD P90 series Shop Manual

Lubrication system

Oil filter
Dipper
Figure 5.3
Kohler oil pressure tester
Figure 5.4
Adapter
Figure 5.5
The 4P90 engine uses a combination pressurized and
splash lubrication system. There is an oil pump in the
Balance shaft
sump that is driven by the balance shaft.
The oil is drawn into the pump through a pre-screen.
The pump pushes the oil through a relief valve then into
the oil filter. From the filter, the oil flows through a passage
in the sump cover until it reaches the crankshaft PTO
bearing. The oil passes through the PTO bearing and is
forced into a passage in the crankshaft. The oil follows this
passage to the crankshaft crankpin. It is forced out
between the crankshaft and the connecting rod.
The rest of the engine is lubricated by the oil mist cre-
ated by the moving parts in the sump.
Oil pump
The oil in the head drains back into the sump through a
passage cast into the cylinder block.

Testing the oil Pump

To test the oil pump:
1. Allow the engine to cool.
2. Connect an oil pressure tester to the engine.
NOTE: There are two methods that can be used to con-
A. Kohler oil pressure test kit #25 761 06-S
1a. Remove the oil filter.
1b. Thread the oil pressure tester onto the oil filter
B. Connecting an oil gauge to the port in the sump
1a. Remove the oil plug from behind the oil filter
1b. Install an M8 x 1.25 male to 1/8" NPT female
NOTE: Mem-co part # "M8 to 1/8 F" can be used.
1c.
nect an oil pressure tester:
nipple. See Figure 5.4.
cover.
base using a 12mm wrench.
adapter on to the oil pressure gauge.
Thread hose and adapter from oil pressure
gauge into the port hand tight.
Lubrication
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