I have a 24 1/2 foot 1999 tioga motor home I recently inherited from my father. It has a Onan Microlite 4000 generator model # 4.0 KY-FA/26100H I can get it to start and run for a couple of minutes if I pour fuel down the gas line then it dies and won't start until I pour more fuel down the line. It has 3/4 of a tank. The person my father got it from had it parked for a couple of years and before that replaced the fuel pump. Is there anything else it could be? Do I have to drop the generator and pull the side cover off to replace the fuel pump or is there an easier way?