Yanmar 3YM30 Sevice Manual page 78

3. Troubleshooting
(3) Engine speed and compression pressure (for reference)
40
35
30
25
20
(4) Measured value and troubleshooting
When the measured compression pressure is below the limit value, inspect each part by referring to the
table below.
No. Item
1 • Air cleaner element
2 • Valve clearance
3 • Valve timing
4 • Cylinder head
gasket
5 • Intake / exhaust vale
• Valve seat
6 • Piston
• Piston ring
• Cylinder
3YM30
3YM20
200 250
Engine speed (min
Cause
• Clogged element
• Broken element
• Defect at element seal
portion
• Excessive or no clearance
• Incorrect valve clearance
• Gas leak from gasket
• Gas leak due to worn valve
seat or foreign matter
trapping
• Sticking valve
• Gas leak due to scratching
or wear
63
300 350
-1
)
Corrective action
• Clean the element.
• Replace the element.
• Adjust the valve clearance.
(See 3.5 in Chapter 3.)
• Adjust the valve clearance.
(See 3.5 in Chapter 3.)
• Replace the gasket.
• Retighten the cylinder head bolts to the
specified torque.
(See 4.2(2)12) in Chapter 4.)
• Lap the valve seat.
(See 4.2(6) in Chapter 4.)
• Replace the intake/exhaust valve.
• Perform honing and use an oversized
part.
(See 4.4(5)-(5-1), (5-4) and (6) in
Chapter 4.)
3.92
3.43
2.94
2.45
1.96
(MPa)
400