Mowed the grass three weeks ago, tractor ran fine. No smoke, no knocking, parked it afterward and shut it down. Today it won't crank. Battery is good with load tester, also connected battery charger and used 125 amp starting function. Getting good headlights and strong starter bump, but no crank. Checked oil and nothing showing on dipstick. Dumped in two quarts to bring level to half a dipstick. Should I try a new starter? What should I do next? Thanks for any and all suggestions. BTW --it's a 35HP diesel Branson