[Tastes like Diesel]

I would imagine that checking all the plastic lines for leaks could be tough to do visually. Perhaps if you have a Mity Vac you could tap into the lines and see if you can a) make the locks work and b) see if the vacuum holds. I would think you could also put a vacuum gage on the pump, unfortunately I don't have the specs for this.

I recently repaired my own car and discovered that a line had let go at one of the connectors inside the door jamb area. The other observation that I made was that the pump would run for 10-20 seconds when activated. I'd be a bit concerned if you pump only come on for a second or two.