Here's what I found to ease the pain of impeller replacement. Spray lubricant into the pump body and rubber vanes. Once the impeller is lubed up, turn the alternator to rotate the engine to break the stiction between the pump body and rubber vanes. Use the same trick on the new impeller to line up the keyway on the shaft. Rotate the engine- which turns the pump shaft-until they both line up. Hope this
helps.