Volvo Diesels have no in tank pump or lift pump. The diesel flows up to a quart of fuel back through the return line in about 2 minutes at high throttle, so you should have plenty of flow in a non return system. I would backflush the fuel line with a mix of gas and diesel fuel system cleaner. Use a pump with a return line(I know some Chevys have em, not sure about ford) if vaporlock becomes an issue. n If you replace the rubber bits (there may be one in the tank), filling the steel lines with biodisel will loosen all deposits in about 8 hours. folow witha high pressure flush.