Fuel only from right tank

Hey yall, Im new to the forum and also to trucking as well. I purchased a 1998 W900 with the 3406e. I've worked out most of the bugs on the truck to get her road ready but this same problem keeps coming back. The passenger tank drains completely and fills the left tank up. I've replaces the vents, lines, return equalizer valve, and I've flushed each line. I have also emptied and flushed out the driver tank thinking maybe trash has been blocking the pickup tube, but it has not. The line from the tank to the water separator is clear, Ive blown it out with air. I'm at a complete loss on what to do. The last thing I can replace is the T fitting for the suction but it is just a simple fitting. Any ideas, comments? I've been racking my brain trying to figure out what else to do. As I said, this is my first truck and hopefully soon I'll get my authority but if I can't fix this problem then I'm dead in the water. Thanks yall and have a blessed day!

 

Thanks guys, I also didn't mention that it doesn't pull fuel from the driver it seems like. It returns the fuel correctly to both tanks

 

I actually just purchased ball valves for the suction and returns, I guess if it works then I'll be happy for now, i may run a equalizer line underneath like the old school trucks if this doesn't make me happy, thanks yall! I'll update if I find anything new

 

So I put a ball valve on the driver return line and closed it off and I watched the field gauge go from half a tank to a quarter tank on the driver side in about 10 minutes so its pulling from both thanks equally it's just not returning equally. I had a local shop install the lines and I look to be identical and link so I guess all that is left is to put an equal icing line from one to the other. I'm not really happy about doing this because it's built to work with the stuff that has right now and putting this line on means that it's not working properly and I am a man who likes things to work that way they were designed to work haha, thanks to those who helped, I look forward to being a member on this site!