My gmc sierra wont start it has fuel to the rack, and new plugs,

You left out a lot of information regarding your problem like the year of the truck, motor size and calif emissions or federal emissions. Im going to assume that your sierra is a late 90s to mid 2000s. If this is the case then a simple fuel rail presure check is in order. (You do not need any tools to perform this task.) (FIRST) , when you turn the key on watch the fuel guage. It should go to the current level of fuel you have in the truck and stay there. If when you turn the key on and the guage begins to go up but suddenly go's back to the "E" then the line pressuer switch (LPS) is decting a "low pressure" ocurence and is shutting the pump down. Its a safety feture in all GMC and Chevy trucks. When this occures the LPS shuts down the power to the fuel pump resulting in a "no power" to the pump situation that I routinaly get at the service center. Most people think its a bad fuse, a relay or the fuel fileter is plugged. (SECOND) Change the filter and test the system again. However the #1 reason for this is a fuel pump that will not pressurize the system to the mimimum pressure required. If this is the case then 99% of the time it's a faulty fuel pump. Depending on your truck emission systems (Califorins or Federal) your rail pressure should be 75 to 95psi for federal and 80 to 100psi for Califorina. Allso you will need to know what your fuel capasity is when ordering a new pump. To find this information there will be a tag on the "main" fule line just above the fuel tank. (where the plastic line meets the outlet) The tag will be yellow with black letters and numbers. If your are ordering a new pump from a dealership the just use the VIN off the truck. The parts counter can use the VIN to retrieve the vehicles information and provide you with a new pump. If you have power to the pump and your line pressue is ok but the truck still will not start you will need to check the fuel injectors. This can only be done using a pulse tool desigined for checking injector systems. I recomend that if this is the situation that you take your truck to a certified mechanic and let them check the injector system. It will be cheeper than buying the tool... software... cables.. etc . I hopped this helped out.

Is or was the service engine light soon on? You may need to have the trouble codes read. In the mean time verify fuel pressure with a gauge, should be in the neighborhood of 54 lbs. If that checks OK, use a "noid" light to verify the injector pulse from the PCM.
Let me know if you need to know how to access the fuel test port and the procedure for checking fuel pressure as well as the injector pulse test.
Good luck, let me know.
Regards,

No fuel from main fuel line? Possible plugged fuel filter? Blown fuel pump fuse? Bad fuel pump or plugged intake sock filter in fuel tank?