Pressure Test - Stihl MS 231 Manual

2
1
: Line up the flange (1)
1118 850 4200 and fit it over the
studs
: Fit the test flange (1)
1118 850 4200.
: Fit the nuts (2) and tighten them
down firmly.
6.2.2 Vacuum Test
Oil seals tend to fail when subjected
to a vacuum, i.e. the sealing lip lifts
away from the crankshaft during the
piston's induction stroke because
there is no internal counterpressure.
A test can be carried out with pump
0000 850 1300 to detect this kind of
fault.
4
1
2
: Connect hose (1) of pump
0000 850 1300 to the
nipple (arrow).
34
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: Push ring (2) to the left
– vacuum test.
: Operate the lever (3) until the
pressure gauge (4) indicates a
2
vacuum of 0.5 bar.
If the vacuum reading remains
constant, or rises to no more than
0.3 bar within 20 seconds, it can be
assumed that the oil seals are in
good condition.
If the pressure continues to rise
(reduced vacuum in the engine), the
oil seals must be replaced, b 6.3.
– After finishing the test, push the
ring to the right to vent the pump.
– Continue with pressure test,
b 6.2.3
6.2.3

Pressure Test

Carry out the same preparations as
for the vacuum test, b 6.2.2
3
: Push ring (1) to the right
– pressure test.
: Operate the lever (2) until the
pressure gauge (3) indicates a
pressure of 0.5 bar. If this
pressure remains constant for at
least 20 seconds, the engine is
airtight.
– If the pressure drops, the leak
must be located and the faulty
part replaced.
To find the leak, coat the suspect
area with soapy water and
pressurize the engine again.
Bubbles will appear if a leak exists.
– After finishing the test, push the
ring to the left to vent the pump –
disconnect the hose.
– Remove the flange
1118 850 4200 from the intake
manifold.
– Install the carburetor, b 12.5
– Remove the flange
5910 855 4201 and sealing
plate 0000 855 8106.
– Install the muffler, b 6.1
– Use a blunt tool to push home the
new plugs – take care not to
damage the plugs.
– Reassemble all other parts in the
3 2
reverse sequence.
1
MS 231, MS 231 C, MS 251, MS 251 C