Engine System
35
Service Manual – PBU Propane Floor Burnisher
Top End, Heads
Compression Test
A compression test is used to determine the
health of the engine The engine pistons make
compression as part of their normal combustion
cycle
You will need a compression tester (pressure
gauge) with a 14mm fitting (standard spark plug
thread) The tester should have a pressure release
valve so you can release the pressure before
disconnecting the gauge
1 Make sure the battery is fully charged and in good condition You
want the engine cranking speed to be consistent throughout the
test
2 Start the engine and bring it up to operating temperature The
engine components fit and seal differently when the engine is hot
versus cold
3 Shut the engine off and close the service valve on the propane
tank You do not want fuel entering the engine for this test
4 To protect the ignition coils and to avoid being shocked, disable the ignition circuit by grounding the
ignition terminal on both coils Disconnect the ignition wire from the coils and replace it with a jumper
to ground
5
Set the throttle selector lever to Fast. You want the butterfly valve in the carburetor wide open to
permit maximum air to enter the cylinder
6 Remove both spark plugs from their cylinders
7
Thread the compression tester into the first spark plug port.
•
It is not necessary to tighten the gauge with tools. Use firm hand-tightening until the gauge is fully
seated
• Make sure the gauge is reading zero before you begin Press the pressure release button to release
pressure (The gauge contains a schrader valve So it will hold pressure even when disconnected )
8 Turn the ignition key to the start position and crank the engine for 5 complete cycles (approximately 5
seconds)
• You should see the pressure gauge pulse with each compression stroke of the engine
•
Make note of at least the first and final compression pulses. The difference between the first and last
pulse may be helpful during diagnostics and evaluation of the test
9 Move the compression tester to the second cylinder and repeat the test Don’t forget to release the
pressure from the gauge before repeating the test
10 Refer to the
section below for analysis, and also to determine whether a “Wet
Test” should be completed
Pressure
Gauge
14mm
Fitting
Pressure
Release
Jumper to
Ground
Ignition
Coil
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