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Home >> Mazda >> 2024 >> CX-90 Turbo Select >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Mechanical (VIN A) (1 Of 6)) >> Compression Inspection [PYUL] >> Inspect Compression Pressure

Inspect Compression Pressure

WARNING: This page is about a different variant/trim than selected.
WARNING:
  • A hot engine can cause severe burns. Turn off the engine and wait until it is cool before removing/installing each part.
  • Fuel vapor is hazardous. It can very easily ignite and cause serious injury or death, and damage to equipment. Always keep sparks and flames away from fuel.
  • Highly pressurized fuel may spray out if the fuel line is cut. Due to the following dangers occurring with a fuel spray, always complete the [Fuel Line Safety Procedure] to prevent the fuel from spraying.
    • Fuel may cause irritation if it comes in contact with skin and eyes.
    • If fuel ignites and causes a fire, it may lead to serious injury or death, and damage to property and facilities.
  1. Verify that the lead-acid battery is in a completely charged condition. (See BATTERY INSPECTION )
  2. Connect the M-MDS to the DLC-2.
  3. Open the hood.
  4. Warm up the engine.
  5. Display the following PID using the M-MDS data monitor function. (Refer to [PID/DATA MONITOR INSPECTION ] in the troubleshooting service information) (Refer to [PID/DATA MONITOR TABLE [PCM] ] in the troubleshooting service information)
    • ENG_RPM
  6. Perform [Fuel Line Safety Procedure] to remove the fuel pump relay. (See BEFORE SERVICE PRECAUTION [PYUL] )
  7. Remove the following parts.
    1. Plug hole plate
    2. Ignition coil/ion sensor (See IGNITION COIL REMOVAL/INSTALLATION [PYUL] .)
    3. Spark plug (See SPARK PLUG REMOVAL/INSTALLATION [PYUL] .)
  8. Measure the compression pressure using the following procedure.
    1. Install the compression gauge to the spark plug hole.
    2. Fully depress the accelerator pedal.
      NOTE: Cranking method is as follows.
      • Cranking begins when the main power is switched ON (READY on) while the brake pedal is depressed.
      • If the main power is switched OFF during cranking, cranking stops.
    3. Crank the engine and measure the following values simultaneously.
      • Compression pressure
      • Engine speed

        Compression pressure 

        G16699350Courtesy of MAZDA MOTORS CORP.
        COMPONENT OPERATIONS

        Component no Refer to
        1 Compression pressure value (kPa {kgf/cm2, psi})
        2 Engine speed (rpm)
        3 Standard
        4 Minimum specification

        Standard: Refer to graph

        Minimum: Refer to graph

        Difference between cylinders: Within 116 kPa {1.18 kgf/cm2, 16.8 psi} [250 rpm]

    4. Perform Steps  1 to  3 for all cylinders.
    5. If a measurement is less than the minimum specification, or there is a cylinder which exceeds the specified difference between cylinders, add a small quantity of engine oil through the spark plug hole and perform Steps  1 to  3.
      • If the pressure increases by adding the engine oil, the piston ring or the cylinder surface is worn, or they are damaged. Perform overhaul servicing.
      • If the pressure does not increase, valve seizure, valve attachment failure, or pressure leakage from the cylinder head gasket might be occurring. Perform overhaul servicing.
    6. If the measured value is high, a malfunction in the electric variable valve timing system can be considered.
  9. Remove the compression gauge.
  10. Install the following parts.
    1. Spark plug (See SPARK PLUG REMOVAL/INSTALLATION [PYUL] .)
    2. Ignition coil/ion sensor (See IGNITION COIL REMOVAL/INSTALLATION [PYUL] .)
    3. Plug hole
  11. Install the fuel pump relay. (See BEFORE SERVICE PRECAUTION [PYUL] .)
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