This demonstration guide answers one field question about a failed inlet valve or air in the pump. Measurements come before parts, and the notes are not a generic equipment FAQ.
Diagnose before replacing parts
Start with pulsation frequency versus rpm. That reading separates a failed inlet valve or air in the pump from adjacent faults that share the same complaint.
If the measurement is out of spec, treat the valves as the primary path. If it is in spec, do not replace the valves just to complete a parts list.
Repair the failed system
The usual correction is the valves, installed to the documented spec for this complaint.
A demonstration shop records the finding so the next technician is not repeating a guess about a failed inlet valve or air in the pump.
Stop before you make it worse
Do not tightening the gun because the pulse "feels like a leak". That shortcut hides the original measurement and creates a second failure.
If the machine still fails after the valves is corrected, convert the visit to a broader diagnosis rather than stacking parts.
Written and published by Ridgeline Small Engine.