1) Except 118 kW motor (160 hp).
Compression check allows you to draw a conclusion about the condition of the engine. Namely, it allows you to establish whether the valves or pistons are in good condition (piston rings), or they are worn out. In addition, the check shows whether the engine should be replaced or it needs to be completely overhauled. To check, a compression tester is required, which is quite inexpensively available for gasoline engines in specialized stores.
Attention: For diesel engines, a compression gauge with an extended measuring range is required.
The greatest information is given by the pressure difference in the individual cylinders. It must not exceed 3.0 bar (for diesel engines 5.0 bar). If one or more cylinders have a pressure that differs from the pressure in other cylinders by more than 3.0 bar (for diesel engines 5.0 bar), this indicates a defect in the valves, wear of the piston rings or working surfaces of the cylinders. If the wear has reached the limit value, the engine must be repaired or replaced.
Gasoline engines
The compression test should be done with the engine warm. The engine temperature must be at least 30°C.
Switch off the ignition.
Injection engine: Remove the fuel pump relay.
Attention: High voltage wire (center wire, terminal 4) pull it out of the ignition distributor and connect it to the vehicle ground using a suitable auxiliary wire. The auxiliary wire must have the same cross section as the high voltage wire and have terminals of the type «crocodile». Do not hold the wire with your hands.
Remove all spark plug tips. There is a special clamp for this, for example HAZET1849. In this case, the capture of tips should be carried out only by metal sleeves.
After that, blow out the spark plug niches in the cylinder head with compressed air and unscrew all the spark plugs with a suitable wrench.
Crank the engine a couple of times with the starter in order to eject carbon deposits and soot from the cylinders.
Attention: shift the gearbox to neutral and apply the handbrake.
Press the compression gauge against the spark plug holes or screw in in accordance with the service manual.
Ask an assistant to completely drown the gas pedal and hold it with your foot throughout the test.
Turn the engine about 8 revolutions until the change in readings on the instrument scale stops.
Check all cylinders one by one and compare the obtained values with the prescribed values.
Then screw in the spark plugs and insert the ignition cable, see chapter «Ignition system».
Diesel engine
Engines from 65 to 80 hp:
Disconnect the fuel switch electrical wire from the high pressure fuel pump.
Remove nozzles, see chapter «diesel engine».
Screw in the compression gauge instead of the injector. At the same time, install an old heat-insulating gasket between the pressure gauge and the cylinder head.
Attention: The given compression values are valid only when the compression is checked with a VAG-1381 compression tester and the presence of the VAG-1323/2A adapter.
Tighten the injectors with a torque of 70 Nm. Caution: Always replace the heat seal between cylinder head and injector. The recess in the gasket must face up when installed. Tighten fuel lines to 25 Nm.
Connect the wire to the fuel switch.
Supercharged diesel engine with 90 and 110 hp.
Disconnect the plug of the fuel shut-off valve at the high pressure fuel pump.
Remove glow plugs, see chapter «diesel engine».
Screw in the compression gauge instead of the glow plug. At the same time, install an old heat-insulating gasket between the pressure gauge and the cylinder head.
Attention: The given compression values are valid only when checking the compression with a VAG-1763 compression tester and the presence of an adapter VAG-1323/18.
Check all cylinders one by one.
Tighten glow plugs to 15 Nm.
Connect electrical wires.
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