Jim,
My engine is an A-4, which is gasoline, not a diesel. Follow Cam's lead on that one. Others may disagree, but my experience has got me thinking it's better to just replace the thing if it's got any age to it. I put $100 worth of replacement parts in it and lots of time, when a brand new
pump costs $200. If you don't fix it, you've got a host of corrosion issues to think about. Good luck.