I removed this pump and stripped it down and found that it was blocked.
Just take it apart by undoing the the end with the hex on it slowly as there is a vavle that jumps out the end that you take off has a valve in it just remove the blue ring and remove slowly this is where i found my blockage. If you want to chech the rest of the pump just lay the parts in order and you will be okay putting it back together.
hst125
June 2021