I pulled the pump and tested it and it is indeed shot. Not only was in only working intermittingly, it looks like it overheated and the fuse holder just before the pump got very hot/distorted. I am surprised it did not blow the fuse.
The pump is a Shurflo 5900-0201 5.7 . I was never pleased with how much noise it made even when it was new. I don't believe this pump is even made anymore and not sure if I wouldn't go with another brand anyway.
Would anyone have a recommendation on a suitable/direct replacement? I read that Aquatec pumps are good.