Hyundai Elantra (CN7): Engine Mechanical System / Repair procedures

Hyundai Elantra (CN7) 2021-2025 Service Manual / Engine Mechanical System / Repair procedures

Compession Pressure Inspection
   
•
If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.
1.
Start the engine and turn the coolant temperature to 80 - 95 °C and stop.
2.
Remove the engine cover (A).

3.
Disconnect the injector connector (A).

4.
Remove the ignition coils.
(Refer to Engine Electical System - "Ignition Coil")
5.
Remove spark plugs.
(Refer to Engine Electrical System - "Spark Plug")
6.
Check the cylinder compression pressure.
(1)
Insert a compression gauge into the spark plug hole.

(2)
Fully open the throttle valve.
(3)
While cranking the engine, measure the compression pressure.
   
•
Always use a fully charged battery to obtain engine speed of 200 rpm or more.
(4)
Repeat steps (1) through (3) for each cylinder.
   
•
If you need to check the compression pressure for more than three times, restart the engine to restore the lubrication condition to be normal and then check the compression pressure again.
Compression pressure
Standard : 1,127.76 kPa (11.5 kgf/cm², 164 psi) (200-250 rpm)
Minimum : 980.66 kPa (10.0 kgf/cm², 142 psi)
Difference between each cylinder : 98 kPa (1.0 kgf/cm², 14 psi) or less
(5)
If the cylinder compression in 1 or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat steps (1) through (3) for cylinders with low compression.
•
If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
•
If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
7.
Install the spark plugs.
(Refer to Engine Electrical System - "Spark Plug")
8.
Install the ignition coil.
(Refer to Engine Electical System - "Ignition Coil")
9.
Connect the injector connector (A).

10.
Some DTCs may exist after the inspection test and may need to be manually cleared with diagnostic tool.
11.
Install the engine cover.
(Refer to Engine and Transaxle Assembly - "Engine Cover")

    Specifications Description Specifications Limit General TypeIn-line, DOHC 　Number of cylinders4 　Bore75.

    Troubleshooting Symptom Suspect area Remedy Engine misfire with abnormal internal lower engine noises.

    Other information:

    Hyundai Elantra (CN7) 2021-2025 Service Manual: Components and components location

    C

    Hyundai Elantra (CN7) 2021-2025 Service Manual: Compressor oil

    Repair procedures Oil Specification1.The HFC-134a system requires synthetic (PAG) compressor oil whereas the R-12 system requires mineral compressor oil. The two oils must never be mixed.2.Compressor (PAG) oil varies according to compressor model. Be sure to use oil specified for the model of compressor.

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