The outlet valve of the air pump is not working.
Car tire inflator pump is a plunger type reciprocating pump, which belongs to the category of positive displacement pumps, which relies on the reciprocating movement of the plunger to compress gas. The structure is that the air chamber is provided with an air valve for intake and exhaust, and the intake valve and the exhaust valve work alternately to achieve the purpose of delivering gas.
If the outlet valve fails, the compressed gas will increase the outlet pressure during the plunger process. When the plunger returns, the gas in the pipeline will return to the cylinder and the pressure gauge pointer will drop back. This causes the pointer of the pressure gauge to swing back and forth.
At the same time, the tire air pressure will be slow.
Remove the air inlet valve and air outlet valve of the air pump, clean and inspect the foreign objects in the valve,
Check the sealing surface of ball, spring and valve seat
Reinstall the air valve and add a small amount of water to test for leaks and confirm that there are no leaks.
Install the air valve to the air pump. The inflation pressure is normal (a slight swing is normal).