This system uses the injection pump as a lift pump as well. It sound like the lift pump part of the injection unit is nor working. If there is a plunger on top of the filter, they are bad for drawing air. If not an air problen you could fit a small electric pump in -line to get the fuel into the injection pump. Done this a few times to this make and works a treat. You can get this from a good motor acc shop at about �25. A lot less than �450 or so to overhaul injection pump.