Can't get my 03 duramax to start. Last time it ran was middle of Jan., went to start it in May it ran about 10 sec. & shut down. I pump up primer pump until it gets hard & wait a few seconds & it goes soft. If I pump up the pump & have someone start it, it will run until I stop pumping. I replaced the fuel lines last summer & fuel filter last summer & ran fine until I let it set over the winter. I replaced the fuel lines on the tank still can't get it to run on it's own. Could you tell me where to go next. If it helps I live in northeast Ohio & the engine heater was plugged in all winter.