Testing Control Valve (Removed From Machine) - Stihl 029, 039 Service Manual

STIHL 029, 039
Top:
Fastening screw on filter box
Bottom:
Control valve bypassed
- Remove the fastening screw from
the filter box. Pull the filter box
with filters off the connector.
- For preparations - see 4.2.1.
- Bypass the control valve by
pushing the air inlet hose onto the
two nipples on the connector.
- For leakage test - see 4.2.2 and
4.2.3.
11.6.5 Testing Control Valve
(removed from machine)
Top:
1 = Air inlet nipple
2 = Air outlet nipple
3 = Connector on cylinder
Bottom:
1 = Nipple 0000 855 9200 with
fuel line 1110 141 8600
2 = Air inlet hose
The control valve can be tested with
the vacuum pump that is used for
leakage-testing crankcases.
- Remove the control valve –
see 11.6.12.
- Push air inlet hose onto the air
outlet nipple and seal it, e.g. with
a scriber.
Leakage test with vacuum pump
0000 850 3500
- Make connection between vacuum
pump and control valve - using fuel
line and nipple as adapter.
- Push tester's pressure hose onto
the nipple.
Note: Leave the cylinder connector
open.
- Pull out pump piston several times
until pressure gauge shows a
vacuum of 0.4 bar (5.8 psi).
Note: Vacuum must not drop more
than 0.2 bar (2.9 psi) within 5 sec.
If it does, the control valve is faulty.
Checking bellows air inlet
function
- Apply vacuum of 0.4 bar (5.8 psi).
- Open the air inlet hose.
Note: Vacuum must drop immediately
(approx. 0.5 sec.) to 0 bar (0 psi). If it
doesn't, the control valve is faulty.
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