There are 2 different possibilities of injection pumps and tools required varies. Stanadyne "DB" series pumps require only a puller to remove the drive gear from the pump shaft. Electronic controlled Stanadyne DE10 pumps need the same puller as well as a timing pin for the flywheel and a timing pin for the pump. As TxJim says, be sure the pump is bad before removal. Is it leaking? Not running properly? Not running at all? If electronic pump, are there any error codes?