Note: During this test, the engine must be at normal operating temperature and the battery must be fully charged.
2. Start by cleaning the surfaces around the spark plugs before removing the plugs. You should use compressed air for this, but you can also use a small brush or even a bicycle pump. The purpose of this procedure is to prevent dirt from entering the cylinders when performing a pressure test.
3. Remove all spark plugs from the engine (see chapter 1, section 32).
4. Lock the throttle valve in the fully open position.
5. Disconnect the power and ignition systems by removing the ECM fuse (see chapter 12, section 3).
6. Insert the pressure sensor into the spark plug hole of cylinder 1 (see illustration).
3.6 Use a threaded pressure sensor to install into the spark plug hole; do not use a sensor with a conical rubber tip - its readings are usually inaccurate, since they depend on how hard you press it with your hand, ensuring a tight seal between the sensor and the combustion chamber
7. Crank the engine crankshaft with the starter for at least seven compression strokes and look at the sensor readings. In a healthy engine, the pressure should build up quickly. Low pressure on the first compression stroke followed by a gradual increase on subsequent strokes indicates wear of the piston rings. Low pressure on the first compression stroke that does not increase on subsequent compression strokes indicates leaking valves or a blown head gasket (the cause could also be cracks in the head). Carbon deposits on the top surfaces of the valve heads can also cause pressure to drop. Record the highest compression gauge reading.
8. Repeat the measurement for the remaining cylinders and compare the results with the specifications in this chapter.
9. If the readings are below normal, add a little engine oil into each cylinder through the spark plug holes and repeat the check.
10. If the pressure increases after adding oil, this indicates wear of the piston rings. If the pressure does not increase significantly, then the leaks are in the valves or through the cylinder head gasket. Valve leaks may be due to burnout of valve seats or contact surfaces, wear, damage or cracks.
11. If the same low pressure is noticed in two adjacent cylinders, then there is a high probability that the gasket between them is torn. The appearance of coolant in the combustion chambers or crankcase may confirm this assumption.
12. If the pressure in one cylinder is 20% lower than in the others, and at the same time there is a slightly uneven idle speed of the engine, then the cause may be wear of the exhaust cam of the camshaft.
13. If the pressure exceeds the norm, this may be due to carbon deposits (carbon) on the walls of the combustion chambers. In this case, it is necessary to remove the cylinder heads and clean them.
14. If the pressure drops or varies significantly between different cylinders, we recommend that you have the engine checked for leaks at an auto repair shop. This test will show exactly where the leak is and how serious it is.
15. Insert the ECM fuse and drive the vehicle to restore the computer's learning memory.