If you remove fuse 4 & jumper the right hand side of fuse 4 holder to fuse 6, you should hear the in-tank pump run. If you don't then it is not functioning. The car usually will run in this condition but it makes the main pump work harder and eventually fail. You may have reached this point.

I usually can tell when the in-tank pump stops working as the main pump gets noisier. I have a '90 240 that has the original main pump in it going on nearly 260k miles. Twice the in-tank pump failed and I noticed just from the fact that I could hear the main pump running while I was driving. Both times fixing the in-tank pump got the main pump running back to it's old quiet self.