Here's a link to a very thorough timeline from the Plano Star Courier:
http://starlocalmedia.com/planocourier/news/christina-morris-investigation-timeline/article_7d76c272-8fac-11e4-ae35-5728221577b8.html
I answered my own question about what time he pumped his gas after finding this timeline. He pumped it at 10:15 AM on the 30th (morning Christina disappeared).
Timeline for background on the 30th from above link (much more at link!):
3:55 a.m. Arochi and Morris seen on surveillance camera entering parking garage.
3:58 a.m. Arochis Camaro leaves the parking garage.
4:08 a.m. Arochis Camaro passed through Custer Road gantry northbound on S.H. 121.
4:47 a.m. Morris phone pings cell tower at 5800 Granite Parkway (north of Shops at Legacy)
4:56 a.m. Arochis phone pings cell tower at 5800 Granite Parkway (north of Shops at Legacy)
5:32 a.m. Arochis phone pings cell tower in 1500 block of Bethany Drive near his home.
6:21 a.m. Sun rises.
10:15 a.m. Arochi pumps gas, inspects trunk and drivers side of vehicle at Allen Kroger, 1212 E. Bethany Drive. He is seen on video wiping down passenger side door and scrubbing back of vehicle with squeegee.
11:00 a.m. Sprint coworker says Arochi arrives to work about 3 hours late, parks in back and appears messed up, walking with a limp. Coworkes says Arochi had visible scratches and a bite mark on his arm, and was complaining his ribs hurt.