Yesterday I picked up a Snapper Z mower with the Kubota D722 engine. From the injector pump, with the fuel lines removed, only one port discharges fuel. The other two do nothing. I removed the pump and all three "fingers" (they look like rollers lifters) move up/down, everything looks clean and the fuel cutoff is ON. Could it have a bad lift pump? For 50 yrs I've been a gas mechanic and unfortunately doesn't know a lot about diesels. Any ideas/suggestions would be greatly appreciated.