My very old L175 is having an oil pressure problem. It will start oil light goes out it will run for a moment, then the oil light comes on, idle or reved up, the lite stays on????? I think that if it were the pump, the light would not go out. I wonder if a port is stopped up and for a moment the pump pressures up and when runs out of oil and the light comes on. shut it down and start it back up, light goes out for a moment then comes back on...... any ideas????? thanks