Fuel Gauge Problem
 

I own 1990 Mustang GT My fuel gauge stays on "E" whenever the car is running even if it has a full tank. But whenever I park it and let it sit for a while it reads the gas level but as soon as I atrt it up it slowly drops back down to "E" my fuel pump is makeing a real loud humming noise could this be the problem because as soon as the car and the fuel pump start up thats when it moves to "E" if anyone has any ideas on what could be the problem please let me know I would greatly appreciate it.

fuel guage...
 

I just replaced my sending unit after having the same problems you described.
It turns out, the worst part was the two-wire connector on top of the sending unit had completely corroded and that's why the signal would vary from full to empty, because of the intermittent ground.
If you have access to a junkyard, I would consider just getting the grey plastic connector housing and a little of the wire and just tie it into you existing wiring.
Obviously, you have to drop the tank but it is only two 15mm bolts holding the retainer straps. The sending unit housing is the one in the middle center.
and it goes w/o saying, make sure you get as much gas out of the car as possible. A mustang tank holds 15.4 gallons and it can be awkward to handle even with a little fuel in it.
If you need a new unit or wiring, http://www.50resto.com has 'em.
Good luck.
no smoking either, but drinking is encouraged.

Thanks alot for the help