"Where is the intank pump fuse?" It's in the fuse compartment just inside the driver's door. I think it might be #7 but check your owner's manual or service manual....all else fails check all the fuses while you're at it.

The hose mentioned is inside the tank connecting the intank pump to the fuel line running out of the tank.

"The car did run better with a full tank,does the gas cap have to seal like on newer cars?Or does the intank pump eliminate that?" Running better with a full tank further oints to a intank pump or hose problem. The gas cap does not have to seal for the car to run. The newer cars have this feature as an emmissions function....a loose cap lets out gas vapors so the new cars give you a warning light if it is loose. A 1980 car will not have emmissions controls nearly that sophisticated.

It's really sounding to me like the intank pump or hose. Check the fuses, then listen to the tank filler pipe while you have someone try to start the car. Let us know what happens.

mormit
85 245DL, 02 S40