Mechanical Fuel Pump and Starter Issues

I'm on my 5th replacement of starter and 4th replacement of the mechanical pump on my 240z in the last 2 months. Is it really this much maintenance? I'd imagine replacing these would normally lead to them working for a while.

The mechanical pumps stop pulling fuel through the lines at some point. Pulling them out and actuating them by hand gets suction, putting them back in does not get fuel up the line. I do not have a second person to test the suction while the pump is installed. They work immediately when they're new, then stop over the course of a day or weeks. Fuel comes up the line just fine (by mouth... if it matters.). I can only imagine the eccentric lobe isn't actually pushing the fuel pump lever far enough to pump... or I'm not cranking the starter long enough to prime an otherwise dry system. What am I doing wrong?

Similarly, I'm doing a lot of dry cranking as I test the car and get it operational. The starters keep going out. I'm cranking for 3-5 seconds and letting rest for 5 seconds (trying to deal with the issue above fuel pump issue usually). Want to know if starter solenoids are this poor or if there's a different process I'm missing.

Edited 46 minutes ago46 min by RobotandtheRoad