Tests And Adjustments; Testing Compression - Yanmar BY Series Service Manual

Tests and Adjustments

TESTS AND ADJUSTMENTS

Testing Compression

The compression tester is used to quickly and
simply check wear and damage primarily to the
cylinder head valves, but also to cylinders and
piston rings.
The results are intended only for comparison
between the cylinders. Lower compression in one
or more of the cylinders is a sign of abnormal wear
or damage.
IMPORTANT
The battery must have an adequate charge
in order to carry out a reliable compression
test. If necessary, connect an additional
battery.
1. Remove all glow plugs. See Remove and Install
Glow Plugs on page 5-22.
2. Disconnect electrical connectors from all fuel
injectors.
3. Turn engine over several times using the starter
motor to remove any loose debris in the
cylinders.
Figure 5-1
4. Assemble special tools OEM No. 11 0 222 and
11 0 236 and install in glow plug port
(Figure 5-1).
BY Service Manual
CAUTION
NEVER hold the key in the START
position for longer than 10 seconds or
the starter motor will overheat.
5. Turn engine with the starter motor until reading
on gauge stabilizes. Note reading on the gauge.
6. Reset gauge and repeat procedure with the
remaining cylinders.
7. Connect fuel injector electrical connectors.
8. Evaluate readings and assess if engine repair is
necessary. If one or more cylinders have a
lower compression pressure, components such
as valves, cylinders and piston rings should be
inspected.
Specification
Item
Cylinder Compression
Pressure
9. Install glow plugs. See Remove and Install
Glow Plugs on page 5-22.
ENGINE
0000201en
Specification
28 ±2 bar (406 ±29 psi)
5-17