No problem on spending $1000's probably 10,000;s of thousands on fuel pumps when they can be fixed...at least for the gumming up/ stuck plunger issue. Its the simplest pump in the world. An electro magnet pulls a small plunger up and a small spring returns... repeat...over and over. Mine's out there exercising right now a year later after cleaning.
Ok from what I can remember...so don't hold me to all of it. Remove pump from generator then turn off the bottom that has hex nut on it. Inside is a small basket type filter, remove. After that is a small clip that holds the plunger and spring in place [again if memory serves me correct] Take that out. Up inside that well where the clip is a small plunger and spring. Mine was stuck so had to mess with it to get it out. I used carb cleaner [2+2] and finally fine emory cloth as it was so nasty. Inside the the well where it goes I used a piece of solid rod [could use wooden dowel] with a slit in it and emory cloth and then a piece of cloth with 2+2 on it. So far Ive fixed 4 pumps this way. I will tell you, on the one generator that the fuel tank had such heavy varnish, I had to clean those pumps about every 2 months even with new clean fuel, I replaced the tank and no issues since. Hope all that makes sense, since its been awhile since Ive had it apart.
To test, you can just shake pump back and forth and here the plunger moving back and forth. You can just hold your finger over the well to test the freeness of the plunger. it should bounce freely on spring. If it doesn't, clean again.