hello,i have a rtv kubota with a 3 cylinder diesel engine,,,,its driving me crazy,when i attempt to start it,i preheat the glow plugs and roll it,it then starts,but,only more a fraction of a second,then,shuts down,then,i need to crank it for a while before it starts,,,,i just installed a new pick up pump,because the old one was not working at all,,, i cleaned the fuel tank out,and installed a new filter,,,,,,the glow plugs are all working,i suspect fuel "drop down" ,i was told there was a one way valve in the lift pump,which prevents fuel from draining back down into the tank,but,i highly doubt if this pump is sophiscated enough to have a valve,or,maybe an air leak in the low pressure side of the system from the tank to the high pressure injection pump,,,,,,can anybody give me advice??? thanks so much in advance