2. The engine must be warmed up to operating temperature, the battery must be fully charged, and the spark plugs removed (see related section). In addition, you will need the help of an assistant.
3. Disable the ignition system by disconnecting the wiring connector from the ignition control module (see related section). Remove the fuel pump relay from the relay box in the engine compartment to temporarily disable the fuel system (see related section).
4. Install a compression gauge in the spark plug hole of cylinder #1.
5. Ask the assistant to keep the gas pedal fully depressed, and then crank the engine on the starter. After one or two revolutions, the compression should increase to a maximum and stabilize. Record the highest value obtained.
6. Repeat the test on the remaining cylinders. Make sure that the gas pedal remains fully depressed.
7. All cylinders should have approximately equal pressure. A difference of more than 1 bar between any two cylinders indicates a malfunction. Note that compression in a healthy engine rises quickly; low compression on the first revolution and its subsequent gradual increase indicates worn piston rings. If compression remains low, the valves or cylinder head gasket are burnt, or the head is cracked. Carbon buildup on the backs of the valve heads can also be the cause of low compression.
8. Compare the obtained values with the data given in the Specifications. If the pressure in one of the cylinders is low, pour a teaspoon of clean engine oil into it through the spark plug hole and repeat the test.
9. If after that the compression temporarily increases, the cylinder or piston is worn out. Lack of improvement indicates that there may be a leak through burnt valves or a burnt cylinder head gasket.
10. Low compression in two adjacent cylinders is almost certainly caused by a blown head gasket between them. The presence of coolant in the engine oil will confirm this.
11. If the compression in one of the cylinders is approximately 20% lower than in the others and the engine runs unevenly at idle, the camshaft cam may be worn out.
12. If the compression is too high, the combustion chambers are probably covered with soot. In this case, remove the cylinder head and clean the chambers.
13. When finished, install the spark plugs and connect the ignition and fuel systems.
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