Has anybody had a complete failure of the engine oil pump? I just disassembled the engine on my YM2310D and found the pump in two pieces. No warning just a sudden loss of pressure. The drive gear and outer pump ring had fallen forward when the pump case split. No other sign of damage
Was the old oil pump aluminum? Many of the GMTs have aluminum pumps, as did some of the early U.S. models such as the YM186 and YM276. When you get a new pump it will probably be all steel.
It was aluminum. Closer inspection today it looks like it has been cracked for a long time. It has some uneven wear on one side of the backing plate and on one side of the rotor and smooth areas where the crack has rubbed back and forth. It looks just like the photos in the link winston1 sent. Parts should be here tomorrow.
Parts arrived today. Pump is installed, engine is back together and running, no abnormal noise. It had oil pressure before it started. It would appear I was lucky and caught it in time.