Compression Tester Rockforce RF-907G09 for Petrol Engines 0–21 bar, 4 Adapters

The Rockforce RF-907G09 compression tester for petrol engines is a mechanical diagnostic tool designed to measure cylinder pressure in the range of 0–21 bar. Supplied with four adapters to fit common spark plug and cylinder thread types, this tester helps assess combustion chamber sealing and engine mechanical condition. It is suitable for workshop use, roadside checks, and routine maintenance to detect low compression caused by worn piston rings, leaking valves, blown head gaskets, or other faults affecting engine performance.

Advantages

The mechanical gauge offers a clear analog display with a broad measuring range up to 21 bar, enabling detection of both minor and major compression issues. A set of four adapters increases compatibility with various petrol engine spark plug and cylinder thread sizes, reducing the need for additional fittings. The robust construction and straightforward mechanical operation make the tester reliable in typical workshop environments without requiring power, batteries, or electronic calibration.

Suitable for

• Measuring static cylinder compression on petrol (gasoline) engines
• Diagnosing worn piston rings, leaking valves, or head gasket failures
• Pre-purchase engine condition checks and routine maintenance
• Workshop and mobile mechanics performing engine diagnostics

Key specifications

• Measurement range: 0–21 bar
• Type: Mechanical analog compression tester
• Includes: Gauge and four adapters for common spark plug / cylinder fittings
• Connection: Threaded adapter fittings for direct cylinder access
• Construction: Durable metal gauge body with protective casing

How to use

Warm the engine to normal operating temperature, then disable ignition and fuel supply according to the vehicle manufacturer’s safety procedures. Remove the spark plug from the cylinder to be tested and screw an appropriate adapter from the set into the spark plug hole until it seats securely. Attach the tester to the adapter and hold the throttle open to allow maximum cranking air. Crank the engine several revolutions with the starter while observing the gauge; record the highest steady reading. Repeat the measurement for each cylinder and compare values to manufacturer specifications or between cylinders to identify relative differences.

Usage recommendations

Use consistent test conditions (engine temperature, throttle position, and number of cranks) for all cylinders and consult vehicle service data for acceptable compression values. If low compression is suspected, perform a wet compression test by adding a small amount of oil to the cylinder to help differentiate between worn rings and leaking valves or head gasket issues.