The air compressor cylinder head intake cavities, discharge cavities or in the discharge pipe are restricted.

Remove the restriction and clean.

The discharge valves are leaking or broken.

Replace or repair the air compressor.

Too much wear is evident.

Replace or repair the air compressor.

Inlet valve is stuck open.

Replace or repair the air compressor.

The inlet valves are worn.

Replace or repair the air compressor.

The system has excessive leakage or usage.

Check and repair as needed.

The engine air filter is dirty (diesel engine).

Replace the engine air filter.

The air compressor air strainer filter is dirty.

Replace the air compressor air strainer filter.