This pilot phase I trial studies the side effects and best dose of CPI-613 when given together with fluorouracil in treating patients with colorectal cancer that has spread to other parts of the body and cannot be removed by surgery. CPI-613 may kill tumor cells by turning off their mitochondria. Mitochondria are used by tumor cells to produce energy and are the building blocks needed to make more tumor cells. By shutting off these mitochondria, CPI-613 deprives the tumor cells of energy and other supplies that they need to survive and grow in the body. Drugs used in chemotherapy, such as fluorouracil, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving CPI-613 with fluorouracil may kill more tumor cells.