Aftermarket fuel pump - not quite the same

My fuel pump failed about 9 months ago and in a hurry I got an aftermarket one for about £20. It did the job fine and appreared to fit well but the engine gradually developed an oil leak. I put this down to the Perkins rear crank seal as these have a reputation for leaking and it was dripping from the sump, but recently its got too bad to ignore - 6" pool in a few minutes. Cleaned everything and waited, it was coming from the fuel pump. Pulled it off and found it was 1/8" thinner than the AC OEM one, just enough for the nuts to feel like they were doing up but actually binding on the stud and not pinching up the gasket. A few thick washers cured it for now, but very annoying and worth looking out for.

Useful, thanks Rob.

When I got a new one I'm pretty sure it had a few different bits and bobs in the box to make it fit different models- yes the box was blue!

Thing is its obvious once you put the two side by side and look at the flanges, but of course I looked very carefully at the bolt spacing and inlet and outlet positions and threads but missed the key difference that's been responsible for a lot (and I mean pints) of oil loss and mess.

Even with the right bits mine leaked, ended up sealing it with a bit of hylomar.