Quote Originally Posted by GasGuzzler View Post
The fuel gauge signal wire is purple terminal W at the instrument panel plug and goes to the sender. From the sender, there is a ground black wire at the top front of the engine (G110) according to my diagram but I've seen plenty of these trucks that have the ground under 13mm headed bolt at the back on the frame. If either of these circuits are open, the gauge will read full. A short to ground in the purple wire anywhere between the tank and the gauge will make it read empty.

Also make sure pink terminal E at the transmission plug is hot all the time the key is on.
-you are right, the ground is at the back of the frame - its ok. purple wasnt open either.