David - If you want to try and salvage the old pump here is what I suggest. I had a similar pump on our 1980 Porsche 928 and because the car sat so long (6 years) it did the same thing - just a "thunk" when you applied 12 volts to it. A mechanic friend of mine told me to try the following before I bought a new one. Get a container about 3" round and about 9" high and take your old pump and remove the fittings on both ends and put it into the container. Fill the container with any good concentrated fuel system (or injector) cleaner so that it covers the pump entirely. Let the pump sit in it for 2 weeks - occasionally moving the pump up and down to force the cleaner into the pump and out. At the end of 2 weeks - take the pump out and dry it on the outside ( leave the cleaner in it) and take a 12volt supply and keep touching it to the terminals (you will get the familiar "thunk" each time) After about the 5th time - mine broke free and started pumping again. Two years later it still runs. I wire wheeled the outside of the pump and sprayed it with a clear coat and she looks good.