A320
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
This [anomaly] was isolated to the APU bleed and even when MX (Maintenance) was still smelling the odor they still signed the aircraft off; given that it went away with engine start. An APU MEL should have been the first thing they did here instead of trying to get the aircraft back out into service. I as Captain was doing the preflight for our flight from ZZZ to ZZZ1. During the preflight we had a fume event once I selected the APU bleed on. The estimated duration of the event was about one minute. The foul smell came on very strong and immediate. Even with our face coverings (per COVID policy) on in the cockpit it still overwhelmed us; it was that strong. I immediately turned the APU bleed off and opened the cockpit windows. Maintenance then came to the aircraft and did their procedure agreeing the smell was throughout the entire aircraft and coming through on both packs. MX did their procedure and once it was returned to service I had them explain what they did. [MX response] an engine run at the gate and a pack burn. Once we stepped back on the aircraft we still could smell the lingering odor and when I asked about it he said; oh it goes away once you get the engine started'. I believe they knew it was still an issue and still signed it off. With the windows open we turned on the APU bleed again and once again the smell came back. This time sending my First Officer and two flight attendants to the hospital. This also resulted in the cancellation of the flight. When I asked about why they didn't just defer the APU in the first place I heard from someone that the high pressure air cart was broken."
A320 Captain reported a fumes event during pre-flight and had Maintenance take corrective action.  Maintenance worked on it and signed it off as functional; but the crew reported it was still an issue as the smell returned resulting in cancellation of the flight.