95 Blazer won't start

Can anyone help?? I have a 95 Blazer 4wd that turns over but will not start, only thing I can tell is that when the key is turned the fuel gauge goes nuts. The pumps does come on, as I can hear it not sure if it stays running when the key is turned over though. Any ideas what this could be, I just put a new sending unit in.

Can anyone help?? I have a 95 Blazer 4wd that turns over but will not start, only thing I can tell is that when the key is turned the fuel gauge goes nuts. The pumps does come on, as I can hear it not sure if it stays running when the key is turned over though. Any ideas what this could be, I just put a new sending unit in.

Little more info needed here.
What engine and engine code?
Was it the in tank sending unit replaced?
Was fuel pump running before sending unit replacement?

Does the fuel pump run engine cranking?

Have you checked fuel pump fuse?
Have you checked for 12 volt power to fuel pump relay key on?
Does relay put out power to fuel pump key on for 2 seconds or engine cranking?
Will the fuel pump run with a 12 volt fused jumper by jumping the fuel pump test plug in or jumping the gray wire to fuel pump?

4.3 V6 I think the engine code is W, and yes it is the tank unit that was replaced. It was originally a New York truck and rust had eaten just about everything on it. And it would run sporadically, one day it would crank and run fine, the next it would not start at all. yes the pump comes on when the key is turned on, and I think it is running when you turn it over. And I have not tried the jumper test. I will be working on it more this weekend, as I am work most of the time. Any ideas would be great

4.3 V6 I think the engine code is W, and yes it is the tank unit that was replaced. It was originally a New York truck and rust had eaten just about everything on it. And it would run sporadically, one day it would crank and run fine, the next it would not start at all. yes the pump comes on when the key is turned on, and I think it is running when you turn it over. And I have not tried the jumper test. I will be working on it more this weekend, as I am work most of the time. Any ideas would be great

Check fuel pressure.
Confirm 59-60 lbs fuel pressure key on prime up or engine cranking.
Also make sure you have good hot blue spark to all plugs engine cranking.

On fuel gauge going nuts check for good tank to frame ground also.