Suburban K2500!!!! Need help?

I put the key in the ignition it turns over but engine will not start . I took it to the Local Dealership Repair shop,they checked everything including the computer hook-up check and could find nothing wrong except the computer relay indicating it it was out of gas when they had proof there was 1/2 a tank of gas.Is there anything that would cause it to misread on the computer check if it were the fuel pump,and if so how do I repair it myself,because I can`t afford to pay $1200 for a new Pump that the dealership says I MAY not need.

Suburban K2500!!!! Need help?photoshop

Need more details....did this happen all of a sudden or have you been having problems leading up to this. What year is the Suburban? How many miles on it? IM me...I can help you with this

Suburban K2500!!!! Need help?symatec

They can tell if the pump is good by reading the fuel pressure. this is easy enough for any shop to do, and should have been done while troubleshooting. It sounds to me like you are getting your chain yanked.

Since you are speaking of computers, the truck is fuel injected, correct? The pump is inside the tank, and if it is half full of fuel, you have a very physically demanding job in front of you.

Tell them to check the fuel pressure. If they can't or won't, get it towed to another repair facility.
You have two possibilities when it will crank and not start: Fuel or Ignition (spark).

Make sure you have spark first, that's the easiest test.

If you do, then you're not getting fuel. I don't know the year of your truck, but there are any number of relays that could be the problem: Injector relay, fuel pump relay.

But most likely it is your fuel pump. $1200 to replace a fuel pump is way high, so I'd start calling some "non-dealership" shops and get quotes.
can you hear the pump run when you turn key on?