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Home >> Mitsubishi >> 2003 >> Lancer Evolution >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 12 (On-Vehicle Service- Except Evolution) >> On Vehicle Service >> Compression Pressure Check
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Compression Pressure Check

WARNING: This page is about a different variant/trim than selected.
  1. Before inspection, check that the engine oil, starter and battery are normal. Also, set the vehicle to the following conditions:
    • Engine coolant temperature: 80 - 95°C (176 - 203°F)
    • Lights, and all accessories: OFF
    • Transaxle: Neutral (P range on vehicles with A/T)
  2. Disconnect the spark plug cables.
  3. Remove all of the spark plugs.
  4. Disconnect the crankshaft position sensor connector.
    NOTE: Doing this will prevent the engine control module from carrying out ignition and fuel injection.
    WARNING: Keep your distance from the spark plug hole when cranking. Oil, fuel, etc., may spray out from the spark plug hole and may cause serious injury.
  5. Cover the spark plug holes with a shop towel etc. Crank the engine for a few seconds to clear debris from a round the spark plug holes. After the engine has been cranked, check for foreign material adhering to the shop towel.
  6. Install the compression gauge to one of the spark plug holes.
  7. Crank the engine with the throttle valve fully open and measure the compression pressure.
    Fig 1: Installing Compression Gauge To Spark Plug Hole
    G01873379Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
    1. Standard value (at engine speed of 200 r/min): 1,618 kPa (234 psi) 
    2. Minimum limit (at engine speed of 200 r/min): 1,176 kPa (170 psi) 
  8. Measure the compression pressure for all the cylinders, and check that the pressure differences of the cylinders are below the limit.
    1. Limit: 98 kPa (14 psi)
  9. If there is a cylinder with compression or a compression difference that is outside the limit, pour a small amount of engine oil through the spark plug hole, and repeat the operations in steps 6 to 8.
    1. if the compression increase after oil is added, the cause of the malfunction is a worn or damaged piston ring and/ or cylinder inner surface.
    2. If the compression does not rise after oil is added, the cause is a burnt or defective valve seat, or pressure is leaking from the gasket.
  10. Connect the crankshaft position sensor connector.
  11. Install the spark plugs and spark plug cables.
  12. Use the scan tool to erase the diagnostic trouble codes.
    NOTE: This will erase the diagnostic trouble code resulting from the crankshaft position sensor connector being disconnected.
    NOTE: If the negative (-) cable has been disconnected from the battery terminal in order to erase the diagnostic trouble code, operate the engine at idle for approximately 10 minutes after restarting.
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