Checking compression in the engine cylinders (Peugeot 307)

Compression is checked with a special compressometer 0188-U for diesel engines. It is also necessary to use a false candle and an adapter FACOM 910.A6 for a compression tester.

Make sure that the starter provides an engine speed of at least 250 min^-1.

Check compression on a cold engine.

Remove the decorative engine cover.

Disconnect the terminals from the battery.

Disconnect the engine control computer.

Disconnect power from glow plugs.

Insulate the glow plug supply wire.

Remove the fuel pump support.

Remove the right cowling bracket.

Remove the glow plug supply rail.

Remove glow plugs.

Install a false candle and adapter FACOM 910.A6 of the compression gauge in the first cylinder instead of the glow plug.

Tighten the false candle to 10 Nm.

Connect adapter to compressometer 0188-U.

Connect the terminals to the battery.

Compression is measured when cranking the crankshaft with a starter. Compression should reach its maximum value in two turns (20-22 bar) and remain unchanged. On a healthy diesel engine, the pressure should build up quickly. Low pressure after the first piston stroke and a slow build-up on subsequent compression strokes indicates worn piston rings. If the pressure is low after the first piston stroke and does not increase during subsequent compression strokes, the cause is a leak in the valves or a leak in the cylinder head gasket.

The permissible difference in compression in different cylinders must not exceed 2 bar. It should be borne in mind that increased pressure gauge readings indicate abundant carbon deposits in the combustion chambers and the need for disassembly and cleaning.

The reason for the drop in compression for a diesel engine is more difficult to establish than for a gasoline engine (the increase in compression after the introduction of oil into the cylinder is not decisive, since the oil can settle on the walls of the swirl chamber or in the recesses of the piston bottom and not get into the area of the piston rings).

If the compression is below normal, then complete the check with leak tests by measuring the leakage rate of air injected into the cylinder under high pressure. This procedure is performed exclusively in a car service.