I have an 88 blazer that I just got done restoring and use it as a DD. The fuel guage only reads down to a half correctly, after that it just stays at a half. Can anyone help me with this? I replaced the sending unit and gauge but no difference. One thing though, when I looked at the wiring diagram I see that there is only 2 wires coming from the sending unit. It was like this on my old sending unit, but the new one had a 3 wire harness?

This is a guess...but i would say the three wires on the new harness are for 1=ground, 2=+12Volts, 3= signal (fuel level). Since you have replaced both the gauge and the sending unit...what happens when you dis-connect the sending unit? does it say at 1/2 level, if so, you have something wrong with either the gauge, the gauge connections where it attaches to the flex backing, or something in the wiring creating a resistance. At least double check the sending unit....i dont know the resistance on that year, but it should read 0~90 ohms EMPTY to FULL or possible 0~30 ohms (someone here should know this) Make sure the gauge has a full 12 volts on one side of it, the other side is feed from the sending unit.

To expand on what BubbaGreen suggested:

If your setup is like the 73-87 trucks, your sending unit should have a ground terminal wire and a signal (sensing) terminal. The ground wire should be grounded at the frame. The sensing wire should lead to the fuel gauge. If you have access to your sending unit, you should be able to measure the resistance of the sending unit using a VOM (meter). As you change the position of the lever arm, the meter should read between 0 and 90 ohms.

The fuel gauge should have three terminals, +12 Volt, Ground and a Sensing terminal. By applying 12 volts between the Postive and Ground terminals of the fuel gauge, place a potiemeter (variable resistor) between the Sensing and Ground terminals. As you vary the resistance of the potiemeter between 0 and 90 ohms, the fuel gauge should read between Empty and Full.

If both check out, you may have a wiring problem. Is it possible that your sending unit lever arm is malfunctioning (hanging up) in the tank?