Never tried this myself but I have read about using an air hose to slightly pressurize the differential to get the fluid into the pump if it will not prime itself. If you were to try this make sure you set the air regulator very low or you could blow the seals out of it. I think I remember using 10 psi but you might want to do some research first. I would hate to give you the advice and have you in more of a mess than you are now.