Measuring compression pressure (Opel Vectra B)

Measuring the compression pressure in the engine cylinders provides information on whether the valves and piston rings are still tight. This affects the engine power, its behavior during cold start, and oil and fuel consumption.

• Warm up the engine (in motion). When the oil is heated, the tightness of the piston rings increases.
• In the engine compartment in the relay box (next to the brake fluid expansion tank) disconnect the fuel pump relay. Otherwise, when measuring the pressure, the engine will be flooded with fuel, which can damage the catalytic converter.
• On a 16-valve engine, unscrew the ignition cable cover on the valve cover.
• Disconnect the wire connector on the DIS ignition module, see also the "Ignition Stop" section in Chapter "Ignition system".
• Put the car on the handbrake, handle
• set the gear shift to neutral.
• Remove all spark plugs.
• Press the rubber cone of the pressure sensor into the spark plug hole of the 1st cylinder (first in the direction of movement) or screw a connecting adapter onto the spark plug thread.
• Have your assistant fully depress the gas pedal. This will fill the cylinders as much as possible.
• Crank the engine with the starter until the maximum pressure value is reached (min. 4 s).
• Take the pressure reading and record it. If you have a pressure recorder with a measuring card, connect to the next cylinder.