If you are having issue with starting after setting for extended periods, then it's just the modern gasoline causing issues. Todays fuels evaporate much quicker and leave behind more stuff when they do. In this case, a small electric booster pump would be a good thing. Only use it to prime the system, have a push button switch that only works if you have your finger on it. They can be placed inline with the OEM pump, fuel can be pulled through them with the stock pump.
If this starting issue is everyday or so, you may have a weak pump. I wouldn't expect to see the glass filter full, they never are. Lawn mower filters are the same way, they are never full. Stock pumps would be in the 3-5 psi range.
