In a fit of enthusiasm I decided to resurrect the coolant pump on my MEC Brown Pedrazoli cut off saw. It's actually a fuel lift pump from some Italian car of (guessing) 1980's vintage. A finger rests on a cam on the motor (originally on the cam shaft in the car) and moves a diaphragm up and down, and above the diaphragm are two one way valves a bit like a heart.
Turns out that the housing that holds the valves, and the diaphragm and return spring are interchangeable with those used on a JCB 3CX 'Project 7 Grey Cab' of 1990's vintage (Perkins engine) - even the retaining screws are the same thread. As it happens I had a shelf spare JCB lift pump - must remember to order another one
AWEM