Won't start with out start fluid

2000 Silverado, V 6, 90,000 miles fuel gauge goes from full to empty at random, won't start without a blast of start fluid. SES light on.
I suspect fuel pump. Will this cause SES light to come on?

With start fluid , starts right up, runs smooth at idle, then runs rough at 1000 rpms.

Thanks for any help.

How about getting the code read, then we can suggest some meaningful advice.

Local mechanic kept truck a week and replaced fuel pump. It started for about 10 days, became hard to start and now will not start even with starter fluid. We have had very rainy weather recently, the truck is kept in a fully enclosed garage but when I raised the hood the entire engine was covered in condensation. Don' t know if this could be a factor.
Service engine light is not own.