New rig, could use some troubleshooting advice.

Going to suggest something real simple on your fuel tanks: are you sure you have two actual tanks?

When a rig gets that old, people do a lot of mods and someone may have taken out the second tank if it sprang a leak, etc.

When you say it does nothing, does it continue to pull fuel from the first tank? If so, then the 2nd tank may not be there or a prior owner bypassed it because it leaks.

If it doesn't pull fuel from anywhere, then it might be the connection has become disconnected.