Cylinder Leakdown Test - Briggs & Stratton 272147 Repair Manual

TM
Vanguard Twin-Cylinder OHV Liquid-Cooled Engine
Section 2 - Troubleshooting
there will be no RPM loss. When the other cylinder is
grounded out the engine will stop.
NOTE
: A twin cylinder engine will run well on
one cylinder as long as the power required for
the application does not exceed the power
produced by the one cylinder.

CYLINDER LEAKDOWN TEST

An accurate method of checking the sealing capability of
the compression components is by using the cylinder
leakdown tester
Tool# 19545
show any variation between cylinders as well as identify
which components may be at fault.
A regulated amount of compressed air is used to
pressurize the combustion chamber with the piston at
TDC on the compression stroke. By listening for air
leaks, it is possible to isolate a specific component or
components causing a problem. An engine in good
condition will display a reading in the green area on the
outlet gauge with a minimum of audible leakage. A
reading in the yellow or red area along with high audible
leakage indicates a problem with the compression
components.
A small amount of air leakage is normal in all engines,
including new engines, providing that the outlet gauge
remains in the green area.
However, if a single component is displaying more
audible leakage, look to that component for a potential
problem. For example, frequently a slight air leak at the
head gasket may not register on the gauge. Obviously
the head gasket would require replacement, as any leak
at the head gasket would have an adverse affect on
engine performance.
NOTE
: When testing water cooled engines,
always remove the radiator cap. If air bubbles
are observed in the coolant while the combustion
chamber is pressurized, this indicates that the
head gasket is leaking internally and/or the
cylinder head or block is cracked.
Compression Testing Using Leakdown Tester, Tool
#19545
1. Run engine for 5 minutes allowing engine to reach
operating temperature.
NOTE
: If engine is cold or cannot be started, air
flow may be higher (gauge readings lower)
. The leakdown test will
because compression components are not at normal
operating temperatures.
2. Remove spark plugs from engine. Disconnect air
cleaner tube and crankcase breather tube at
carburetor intake elbow.
3. Rotate crankshaft in direction of operation until
piston for cylinder being tested is at top dead
center of compression stroke.
4. Assemble the clamping tool to the crankshaft.
Torque screws to
3/8" breaker bar into slot of clamp or install screw
through slot into bolt circle hole in crankcase
cover, Fig. 22.
Fig. 22
NOTE
: The crankshaft must be held with the
piston at top dead center to seal the combustion
chamber and eliminate any chance of rotation. If
the engine is installed in an application, many
times the equipment can positively lock the
crankshaft from moving.
. Insert drive end of a
150 in. lbs
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