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Instruction Manual
BGS technic KG
Bandwirkerstr. 3
42929 Wermelskirchen
Tel.: 02196 720480
Fax.: 02196 7204820
www.bgstechnic.com
Art. 8235
Compression Tester
General
The compression tester is a valuable tool for the diagnosis of engines, which can be both age-related
and tear as well as leakage of the piston rings and valves notice. The compression tester has a wide
range of application such as. e.g. Diagnosis of cars, motorcycles and machines with 2- or 4-stroke
engines.
Safety
Beware of tests on hot engines!
By hot exhaust manifold or other hot engine parts cause burns!
Instructions
1. Start the engine for about 15 minutes until it reaches normal temperature.
2. Turn off the engine.
3. Disconnect the power to the ignition coils and fuel pump. The separation of the ignition cable
alone can lead to damage of the modern ignition systems.
4. Remove all the spark plugs from the cylinder head, put these in the order in which they were
developed. This can be helpful for further diagnosis.
5. Clean the spark plug threads with e.g. Compressed air.
6. Screw the appropriate adapter or the hose directly into the spark plug threads. Tighten the hose
and adapter by hand only. Do not use tools!
7. Now start the engine for at least 4 seconds, and give full throttle until the pressure on testers no
longer rises.
8. Note the maximum value and repeat the test on all remaining cylinders (step 5 to 8)
Test result
At intact cylinders the pressure increases directly on start up to a peak value.
Check all cylinders by manufacturer's instruction, the difference between them may be up to 10%.
When a cylinder has no pressure and the spark plugs have traces of oil, the piston should be
checked for damage. At high combustion temperatures, for example by uncontrolled combustion
(coal oil on the spark plug) can cause damage to the piston (pitting) lead.
If the value is less on two adjacent cylinders than the value of the other cylinders, there is a
defective cylinder head gasket in the transition zone between the two cylinders. This is also true if
there is water and / or oil at the spark plugs.
If one cylinder has a lower pressure as indicated by the manufacturer, give a little engine oil into
the cylinder and run the compression test again. If the pressure rises sharply, the piston rings are
worn. If the pressure remains the same low level, the defect is a leaky valve or a defective
camshaft.
If the pressure indicated on all cylinders less than that stated by the manufacturer, the motor has
age-related wear and for diagnose the engine must be disassembled and measured.
Install all the spark plugs and cables in the correct order.
Note:
For all tests should always vehicle specific data are available.
If in doubt, consult a specialist
