One for the Yamaha 4 Stroke/Fuel System Gurus

Take the hose off the output side of the bulb. Have a container handy to catch fuel. Start squeezing the bulb. Oddly mine pulled fuel most easily horizontally. Once air was out of the supply side, I connected the hose to the output side. Problem solved until I couldn't overcome the air pressure on the delivery side. Once I turned the ignition on and the fuel pump started, I was able to squeeze the ball a few more times and filled the engine separator bowl and likely the VST.
No issues since.

I have the same issue with my primer bulbs. Bought new ones. Same issue. Remember primer bulbs are not designed for pumping air and if they are empty they will not work very well. Sometimes they do sometimes they don’t! However the low pressure fuel pump will suck fuel through them easily. Continue to run your motors and if they run fine don’t worry about the fact that your primer bulbs won’t suck fuel from your water separators. I fill my water separators up 3/4 on install, but don’t always and never had a problem. Your original problem may have been the bent canister all along and now you have new primer bulbs and as long as the engines work throughout the range you should be good!

I have had this problem and in the end removed the anti-siphon valve. To get the filter full, I use a vacuum pump to get it full and fuel to the bulbs..