ENGINE TESTS B. ENGINE COMPRESSION TEST : I. Description : • The engine compression test provides the technician with information regarding the condition of the engine piston rings/block, cylinder head gasket, and the valves. Before performing the engine compression test, make certain the loss of power or overheating cannot be attributed to something simple such as improper fuel, obstructed air filter, low oil or coolant level, or dragging brakes. Test Procedure : • If possible, bring the engine up to operating 1. temperature (approximately 80° - 90° C) by starting and driving the vehicle for several minutes. Make sure the vehicle battery is fully charged. 2. Remove the air filter element. 3. Label the spark plug coils and remove all spark 4. plugs from the engine. Install an engine compression test gauge (0 to 5. 25 bar) into the number one engine cylinder spark plug port. . (Remove fuel injector connections to avoid fuel injection). Depress the clutch and accelerator pedal fully 6. and crank the engine Have an assistant read and record the highest 7. pressure obtained on the gauge. Follow steps 5 through 7 for the three remaining 8. cylinders, recording the pressure obtained on the gauge. Compare the compression reading obtained for 9. each engine cylinder. The minimum compression is 12±1 bar. If the compression reading in a cylinder is 10. below 10 bar, there may be leakage past the piston rings or valves. Squirt a several drops of oil into the cylinder bore and perform the compression test again. If the compression improves after several 11. drops of oil are squirted into the cylinder bore, the piston rings are most likely leaking. If the compression does not improve, the valves may be allowing leakage. If the compression between two adjacent 12. cylinders is below the minimum, there may be a leak in the head gasket between the cylinders. If suspecting a blown head gasket check the engine oil and coolant for signs of contamination. If coolant mixes with the oil in the sump, the oil will appear to be a dark, milky, substance. If cylinder compression is leaking into the coolant, bubbles will appear in the coolant reservoir while the engine is running. CAUTION Use care not to damage the threads in the spark plug port when installing the compression test gauge adapter. ENGINE 1.2L BSVI PHASE-2 47
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