I don't think even a Rover engine knows what sort of pump is feeding it, Graham. so long as it's getting the right volume at the right pressure, I can't see that it would be bothered if a pump from a Ford supplier was used
But for authenticity, I guess Rimmer Brothers would have the right one, although I suspect that it's an aftermarket pump anyway as I think the Rover 800 series used an in-tank pump. Is it the single point or mulitpoint injection engine?
