On 7/2/79, MPTA-098 suffered major structural damage due to a fractured fuel valve on engine 2002. Testing resumed two months later but a liquid oxygen high speed turbopump failed 9.7 seconds into a scheduled 510 second test. It wasn't until 12/17/79 that a complete static firing was accomplished that included 3 main engines running up to 100 percent of rated thrust for 554 seconds.
On 1/17/81, just three months prior to the scheduled STS-1 launch date, MPTA-098 successfully demonstrated a 625 second firing. The three flight rated engines from Columbia were removed, shipped to NSTL, and installed on MPTA-098 where they successfully completed a 520-second flight mission demonstration test. The engines were then shipped back to KSC and installed on Columbia where they successfully performed a 20-second Flight Readiness Firing (FRF) on 2/20/81. This cleared the way for the launch of STS-1 on 4/12/81.