Complex sentence: Due to money issues and the constant uncertainty of racing in Champ Car, Patrick Racing jumped over the IRL in 2004 running Al Unser, Jr. until his mid-season retirement and then Jeff Simmons, Jaques Lazier, and Tomáš Enge.
Split into simpler sentences: Due to money issues and the constant uncertainty of racing in Champ Car, Patrick Racing jumped over the IRL in 2004. They ran Al Unser, Jr. until his mid-season retirement and then Jeff Simmons, Jaques Lazier, and Tomáš Enge.