Tank Vent; Testing; Removing And Installing - Stihl MS 271 Manual

12.10

Tank Vent

12.10.1 Testing

If problems occur on the carburetor
or the fuel supply system, also
check and clean the tank vent and
replace it if necessary. Check
function by performing pressure and
vacuum tests on the tank via the fuel
hose.
– Open the fuel tank cap and drain
the fuel tank, b 1.
– Close the tank cap.
– Remove the carburetor, b 12.5
1
: Push the
nipple (1) 0000 855 9200 into the
fuel hose (arrow).
Models with manual fuel pump
1
2
: Use a suitable plug (2) to seal the
fuel suction hose (1).
MS 271 C, MS 291 C
Vacuum test
1
: Push the ring (1) to the left and
connect the pump (2)
0000 850 1300 to the
nipple (arrow)
– create a vacuum in the fuel
tank.
Equalization of pressure takes
place via the tank vent. There must
be no buildup of vacuum in the tank.
– Clean the area around the tank
vent.
– If necessary, install a new tank
vent or tank, b 12.10 or
b 12.11.5.
Pressure test
1
: Push the ring (1) to the right and
connect the pump (2)
0000 850 1300 to the
nipple (arrow)
– pressurize the fuel tank.
– Operate the pump until the
pressure gauge indicates a
pressure of 0.5 bar. If this
2
pressure remains constant for at
least 20 seconds, the tank,
including the tank vent, is airtight.
If the pressure drops, the leak
must be located and the faulty
part replaced.
– Reassemble in the reverse
sequence.

12.10.2 Removing and Installing

– Remove the shroud, b 6.4
: Take out the screw (1).
2
: Press the tank housing (1)
downwards and use wooden
block (2) 1108 893 4800 to
maintain the gap.
1
1
2
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