This demonstration guide answers one field question about vacuum collapse in the tank as fuel is consumed. Measurements come before parts, and the notes are not a generic equipment FAQ.
Diagnose before replacing parts
Start with cap-vent airflow and tank vacuum after a stall. That reading separates vacuum collapse in the tank as fuel is consumed from adjacent faults that share the same complaint.
If the measurement is out of spec, treat the fuel cap vent and tank vent path as the primary path. If it is in spec, do not replace the fuel cap vent and tank vent path just to complete a parts list.
Repair the failed system
The usual correction is the fuel cap vent and tank vent path, installed to the documented spec for this complaint.
A demonstration shop records the finding so the next technician is not repeating a guess about vacuum collapse in the tank as fuel is consumed.
Stop before you make it worse
Do not puncturing the tank to "fix" vacuum. That shortcut hides the original measurement and creates a second failure.
If the machine still fails after the fuel cap vent and tank vent path is corrected, convert the visit to a broader diagnosis rather than stacking parts.
Written and published by Ridgeline Small Engine.