According to INDYCAR, the #14 had too large of a fuel cell, failing to comply with Rule 14.7.2.
14.7.2 Fuel System (Updated March 15, 2012 via Bulletin)Simon Pagenaud's #77 car failed the same rule following Iowa, but was fined just $5k because it was found to have no effect on the race results.
The maximum capacity of the fuel cell shall be 18.5 U.S. Gallons.
"We felt the discrepancy in the size of the fuel tank was enough that it potentially could have provided a track position advantage and the penalty is reflective of that," said Will Phillips, vice president of technology, INDYCAR.
A.J. Foyt Enterprises may challenge the ruling.