Air Carrier Captain reported a strong 'dirty socks' odor upon arriving at the aircraft. The Captain submitted an AML discrepancy; a company fumes report and assisted with an engine run before deplaning due to physiological symptoms.

Narrative

Upon arriving at the aircraft; I immediately detected a familiar and strong 'dirty sock' odor. During preflight; the smell seemed very strong to me; and I asked my First Officer if he smelled it. He agreed the smell was strong; but he is also new to the aircraft and may not have experienced the smell before. I suggested that I start the APU and open the bleed to see if the smell intensified or not. After opening the APU bleed; the odor increased a great deal. The fumes were uncomfortable to breathe; and bothered my throat. I shut down the APU and called Maintenance. I subsequently made an entry in the AML. I then completed the smoke; odor; fumes report. The first step of the report directed me to remove my crew from the aircraft; which I did. Contract Maintenance asked if I would help with an engine run. I agreed; but being a new captain; I did not fully understand the implications. I performed an engine run; but after about five minutes of the requested ten minute run; I told the Mechanic that I could not tolerate the fumes any longer and shut down the engine. A few minutes later one of the Mechanics asked if I would be willing to perform another engine run using external air. I refused. I later learned from a Duty Pilot that a safety briefing should have occurred between Maintenance; Contract Maintenance; and me. I did not receive a safety briefing; and I blame myself for not researching what the FOM had to say about engine runs for maintenance. [The most likely] cause [was the] Causal factors include an unknown defect in the APU.I appreciate that Maintenance; Dispatch; and the Duty Pilot who called me trusted my judgment. I have been qualified on the A320 for over X years; and I am very familiar with the dirty sock smell that indicates a serious problem. I think the known issue of fumes on the A320 fleet should be addressed more thoroughly.