Pump for Dewalt DXPW3025. The pump is a Simpson Cleaning AAA 90037. There is an oil seal that goes into the end. In the picture it it is part 251. It just slips on. 252 and 253 are already on (they never came off).
The seal came loose from the shaft and oil leaked. I put the seal back on and it worked for a while, the the seal cam off and oil leaked. I have ordered a new seal. Could it be that the seal is just old? It looks alright. There seems to be no way to put it in except just slip it on the shaft and place it in. There are no other clips, etc. The clip shown in diagram is behind the seal next to the bearing.