Note. During this test, the engine must be warmed up to normal operating temperature and the battery must be fully charged.
2. Start by cleaning the surfaces around the spark plugs before removing the spark plugs. You should use compressed air for this, but you can get by with 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 throttle fully open.
5. Shut off the power and ignition systems by removing the ECM fuse (see chapter 12, section 3).
6. Insert the pressure sensor into the hole for the spark plug of the 1st cylinder (see illustration).
3.6. Use a threaded pressure gauge to fit into the spark plug hole; do not use a sensor with a tapered rubber tip - its readings are usually inaccurate, because they depend on how hard you press it with your hand, ensuring the tightness of the junction of the sensor and the combustion chamber
7. Turn 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 worn piston rings. Low pressure on the first compression stroke that does not build up on subsequent compression strokes indicates a valve leak or a torn cylinder head gasket (Cracks in the head could also be the cause). Carbon deposits on the upper surfaces of the valve heads can also lead to a drop in pressure. 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 reading is below normal, add a little engine oil to each cylinder through the spark plug holes and recheck.
10. If the pressure increases after adding oil, this indicates wear on the piston rings. If the pressure does not increase significantly, then leaks occur in the valves or through the cylinder head gasket. Leaks through valves can be associated with burnt out seats or valve contact surfaces, their wear, damage or cracking.
11. If equally 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 idling of the engine, then the cause may be the wear of the exhaust camshaft cam.
13. If the pressure exceeds the norm, then this may be due to the coating of the walls of the combustion chambers with soot (carbon). In this case, it is necessary to remove the cylinder heads and clean them.
14. If the pressure drops or differs significantly in different cylinders, we recommend that you have a leak test in an auto repair shop. This test will tell you exactly where the leak is and how bad it is.
15. Insert the ECM fuse and drive the vehicle to restore the computer's learning memory.