2005 S300 skid steer. Primer bulb keeps losing prime. I'll prime it, turn over ignition, fires right up. But starts to die within 10 seconds unless I run back and continually squeeze the primer bulb. If I sit there for like 10 minutes squeezing the primer bulb with the engine running, it eventually grabs and runs with no problem with no more primer bulb needed. Put a fresh fuel filter, no difference. Suggestions? Thanks in advance for any help.