the one came stock with ur 3 cyl carby engine.
its fitted on engine and works with engine movement.
i think, ur mechanic has installed an EFI or inline fuel pump, which keeps working all the time and dies due to getting overheated.
i think, ur car used to have a CNG setup, and the fuel pump died due to being working dry while being on CNG.
try to find a re build kit for the fuel pump else find a new replacment.