Service Manual

Compression Pressure
1. Make sure engine is warm (coolant temperature 80 –
95C (176 – 203F), all lights and accessories are OFF
and transmission is in NEUTRAL.
2. Remove spark plug caps (3).
3. Remove spark plugs (3).
4. Install a compression gauge in a spark plug hole.
5. With throttle held open, crank engine and measure
compression pressure.
Figure 46
Compression pressure 1,250 Kpa (178 psi) at 400 RPM
Limit 960 kPa (137 psi) at 400 RPM
6. Measure compression pressure for all cylinders.
Make sure pressure differential for each cylinder is with-
in specified limit.
Liquid Cooled
Gas Engine
Pressure differential limit 100 kPa (14 psi)
7. If a cylinder’s compression or pressure differential ex-
ceeds the limit, add a small amount of engine oil through
spark plug hole and repeat steps 4 – 6.
If addition of engine oil causes and increase in com-
pression pressure, the piston ring and/or cylinder
wall may be worn or damaged.
If addition of engine oil does not cause any increase
in compression pressure, the cause may be valve
seizure, poor valve contact or pressure leaks
through head gasket.
Intake Manifold Vacuum
1. Make sure engine is warm (coolant temperature 80 –
95C (176 – 203F), all lights and accessories are OFF
and transmission is in NEUTRAL.
2. Install a vacuum gauge.
3. Check to make sure intake manifold vacuum is at the
standard value when the engine is at standard idle
speed.
Intake manifold vacuum 60 Kpa (450 mm Hg, 18 in. Hg)
Figure 47
Workman 3000/4000 Series Page 3
– 33 Liquid Cooled Gas Engine