Compression Inspection

WARNING:

Hot engines and oil can cause severe burns. Be careful not to burn yourself during removal/installation of each component.
Fuel vapor is hazardous. It can very easily ignite, causing serious injury and damage. 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.

Verify that the battery is fully charged. (See BATTERY INSPECTION .)
- Recharge it if necessary. (See BATTERY RECHARGING .)
Connect the M-MDS to the DLC-2.
Warm up the engine to the normal operating temperature.
Display the following PIDs using the M-MDS data monitor function. (See PCM INSPECTION .)
- RPM (engine speed)
Perform "Fuel Line Safety Procedures". (See BEFORE SERVICE PRECAUTION .)
Remove the following parts.
1. Plug hole plate. (See PLUG HOLE PLATE REMOVAL/INSTALLATION .)
2. Ignition coil/ion sensors. (See IGNITION COIL/ION SENSOR REMOVAL/INSTALLATION .)
3. Spark plugs. (See SPARK PLUG REMOVAL/INSTALLATION .)
4. Fuel pump relay
5. Fuel injector relay

Measure the compression pressure using the following procedure.

Install the compression gauge to the spark plug hole.
Fully depress the accelerator pedal.
NOTE:
- The cranking method is as follows.
  - When the ignition switch is pressed with the brake pedal depressed, cranking starts.
  - When the ignition switch is pressed during cranking, cranking stops.

Crank the engine and measure the following values simultaneously.

Compression pressure

Courtesy of MAZDA MOTORS CORP.

Standard: Refer to the graph.

Minimum: Refer to the graph.

Maximum difference between cylinders: 153 kPa {1.56 kgf/cm² , 22.2 psi} [250 rpm]

NOTE:

Because the SKYACTIV-G 2.5T retards the intake valve closing timing, compression pressure is low.

Perform Steps 1 to 3 for all cylinders.
If the measured value is the threshold or less, or if there is a cylinder which exceeds the specified maximum difference between cylinders, add a small amount 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 malfunction, or pressure leakage from the cylinder head gasket might be occurring. Perform overhaul servicing.
If the measured value is high, it is possible that there is an error in the electric variable valve timing system.