Car Cylinder Pressure Gauge, Auto Repair, Gasoline, Diesel, Motorcycle, Cylinder Pressure Tester, Engine Cylinder Pressure Gauge, Car Inspection

Cylinder Pressure Gauge Instructions

I. Procedure

1. Start the engine and allow it to reach normal operating temperature.

2. Loosen all spark plugs by one or two turns, then use the starter motor to turn the engine over (without actually starting it) for 5–10 seconds. This will dislodge any dust around the spark plug seats, preventing it from falling into the cylinders.

3. Carefully remove all spark plugs. A visual inspection of the spark plugs can reveal many issues: for example, oil on the spark plugs indicates damaged piston rings or worn valve guides, while burnt spark plugs indicate a vacuum leak.

4. Fully open the carburetor throttle and observe the results.

5. While cranking the engine with the starter, press the pressure gauge’s rubber heat-resistant cone firmly against the spark plug hole.

6. Use the starter motor to turn the engine over until it completes four compression strokes. During each compression stroke, the gauge reading will show a slight pulse; pay close attention to the readings during the first and fourth strokes. Ensure the battery is fully charged and the starter motor is in good condition, turning the engine over at a normal speed; if the starter motor turns the engine over too slowly, it will lead to incorrect results.

7. After reading the gauge, pull the vent valve at the end of the cone to relieve pressure.

II. Interpretation of Results

(1) When the engine is in good condition

1. First stroke: 50–70 psi

2. Final stroke: within the rated technical specifications

3. Cylinder-to-cylinder variation is less than the rated tolerance

Note: The difference in pressure between cylinders should not exceed 10–15 PSI (for Ford vehicles, the lowest value should be less than 3/4 (75%) of the highest value).

(2) When the engine has issues

1. Low pressure during the first stroke and a total pressure of only 10–20 PSI per stroke indicate that a valve is stuck or a valve seat is burnt out

2. Low pressure in one or all cylinders. Inject a small amount of engine oil into the cylinder to check for damage to the piston rings or cylinder walls, or to see if oil is blocking the fine gaps around the piston rings. If the reading remains low, the problem lies with the valves or the cylinder head gasket. If there is only a slight increase, the piston rings, valves, or cylinder head gasket are damaged—or all three may be faulty.

3. Higher-than-normal pressure is caused by excessive carbon buildup in the cylinder.

4. In an engine where the cylinder has been repaired and new piston rings installed, if the reading is low, it may be due to improper installation of the piston rings.