[Oldsguy]

leaking fuel or oil? I think you mean oil. Then the pump itself really isn't leaking the mating surfaces between it and the front of the block are. The block surface must be free of any old gasket debris or old silicone, etc. That area is hard to get to when the engine is installed with everything in the way, sort of a tight fit. I use a small mirror and flashlight to reflect light directly onto the surface and allow me to see how clean the surface is. Use a small scraper, small bits of emery cloth on the ends of my fingers etc to clean it off. If you have room (I doubt it) use a dremel tool with a buffing attachment, that is the one that is made of layers of white cotton pressed together. I did this but the fan and alternator and all the other stuff was off the engine. It turns fast enough to provide enough friction to clean the surface. Then clean with denatured alcohol or your favorite solvent. It really has to be clean. The same goes for the fuel pump mating surface but usually if it is new that isn't a problem. I pre-apply the gasket to the pump first with silicone and let it set up. That way it won't slip on me when I install it, a little silicone on the other surface and on it goes. If it still leaks, you may have a bad gouge or someone in the past has really worked on that surface and given it a depression so it isn't flat.