So, after getting a full parts breakdown (numbers only, no descriptions) from a friend of mine, I went at it. Came apart easily. Was careful with the Orings. This engine came out of an 86 E-28/2 which was abandoned at the marina I use. I hope that the owner didn't abandon it because the engine didn't work. The solution was a good cleaning of the internal parts of the pump. One of the two internal elements worked fine so left that one alone. I disassembled the other and found that two of the parts that produce the high pressure were frozen. Removed them (basically a tube with a piston) and let them soak in acetone overnight. Still couldn't get them apart. Tried a bit of heat and that didn't work. The top of the tube had a small opening giving access to the top of the piston. I ground down a brass threaded rod so it would fit in the opening and gently drove the piston out. Both parts were pretty gummed up and it took quite a while of soaking and working the parts to get everything cleaned up and moving freely again. I have reassembled the pump. I'll put everything back together tomorrow and hopefully the engine will run.