GE water heater pilot wont stay on. I replaced the thermocouple, fitted right, positioned correctly in pilot assembly. Pilot orifice clean. The light goes out immediately after Ive depressed it for 2 min or more. Flame is blue, good size, no draft. Please help.

Usually if they won't re-light it's a problem with the orifice on the pilot itself. The thermocouple won't cause it to re-light but it will prevent it from staying on after being lit. Just make sure you have valve set to pilot when you press the red button down to light. You can take out the burner by removing the gas and thermocouple lines, unscrew the orifice and use like a wire brush bristle to clean out the hole in the orifice.

Open following links for pilot and troubleshooting resources:
Problem could be bad thermocouple, thermocouple not sitting in pilot flame, pilot orifice needs to be cleaned, water heater needs more air, dirty air intake, hot attic environment, backdraft blowing out pilot, or bad gas control valve.
If you get flame, then ECO is not tripped.
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot
http://waterheatertimer.org/How-to-test-water-heater-thermocouple.html
http://waterheatertimer.org/pdf/How-to-replace-thermocouple.pdf

I would remove pilot light assembly and clean orifice and blow out gas line to pilot. Check to see that thermocouple is centered in pilot flame. It is possiblethat your gas valve is bad but it is also possible that you got a defective thermocouple. I would change the thermocouple again as they are much less expensive then the gas valves. The next time when you are sure you have the thernocouple mounted as close to the center of the pilot flame hold the pilot button down for several mins. If none of this works then you may have to change your gas valve.Thank you.

Thermocouple has failed., replace thermocouple or dirty pilot assembly, not enough heat being genrated to produce the 30 mili volts D.C. current to hold the pilot valve open. Clean pilot orfice. Remove assembly and pilot tubing from gas valve. Blow into pilot tubing to remove dirt.. Make sure pilot flame is engulfing the thermocouple.

I would remove burner assembly and clean pilot orifice to make sure you are getting strong pilot flame. I would also check the position of thermocouple. If it is laying on bottom of combustion chamber I have had this make new thermocouples go bad.
Also check the height of flue where it goes thru roof. With the newer water heaters with bottom air intake I have had problems with the pilot being blown out due to no other way for air to escape if you have a downdraft. Flue should be higher then highest point on roof.
If all else fails I would replace gas valve. Hope this helps you. Thanks

Some things to check:

Make sure the thermocouple is squarely in the pilot flame and that the pilot flame is large enough to envelop the thermocouple. A weak pilot can be caused by gas pressure or a carboned-up pilot orifice (where the gas comes out). The orifice may need to be cleaned. Ordinary automotive carburetor cleaner will work. Don't try to stick objects into the orifice - damage may result. If you need to perform this step, make sure the gas is turned off to the heater first.

Make sure the other end of the thermocouple is clean and tight in the gas valve.

Hold the pilot plunger down for at least a minute to be sure to give the thermocouple enough time to heat up.

Check the following:

See if your heater has a pilot gas adjustment valve. It should be on the gas control valve somewhere. Not all heaters have these. It will be a screw on the valve that can be turned.

Make sure the thermocouple sensing bulb is squarely in the pilot flame and also check that the fitting where the other end of the thermocouple connects to the main gas valve is tight.

Check the pilot gas orifice (where the pilot gas comes out) for carbon build up - you may need to remove the pilot gas line and thermocouple assembly to get to this. This problem is pretty common.

Check the gas pressure to the heater. Run the hot water in the dwelling until the hot water heater starts. Check the flame on the main burner and see what color it is - it should be blue with possibly some yellow-tipped flames. If not, there could be a problem with the gas pressure at the heater or venting. If the heater has a gas pressure regulator, it may be out of adjustment or defective.

Finally, and this isn't very common, the pilot light can be extinguished if there is a draft problem, usually associated with an issue with the flue pipe venting system for the heater or another nearby gas consuming appliance.

This can be two common things:

1. Carbon buildup at the pilot orifice (where the gas comes out). This can be cleaned with carburetor cleaner, but make sure the gas is off first (important!).

2. The thermocouple is either bad, displaced or it too is carboned up like the pilot assembly described above.

If you clean everything and the pilot still keeps going out, replace the thermocouple. Make sure the thermocouple is squarely in the flam path.

This sounds like a dirty pilot jet orifice or a weak thermocouple. The pilot orifice can carbon up (natural gas is a fossil fuel), become weak and keep going out whenever the main burner lights, which causes a pressure drop in the gas line. The thermocouple can also become dirty and not sense properly.

The pilot light assembly should be cleaned. The gas must be turned off and it's best if the pilot assembly can be removed. Automotive carb cleaner can be used to clean the orifice. Do not try to insert any object into the pilot orifice valve as this can result in damage.

If cleaning does not resolve the problem, replace the thermocouple first. Make sure it is installed correctly and is squarely in the pilot flame.

The pilot assembly should look similar to the pic above. Depending on where you live, you may be required to hire a certified plumber to replace the parts. If not you can do it your self. Keep in mind if it's not staying lit you also need to check the thermostat and the thermocoupler before replacing the pilot assembly. There is a good chance it is just the thermocoupler going out. It is one of the first things to check when troubleshooting a pilot light problem with a gas water heater. A thermocouple determines if the pilot light is lit. If it's not lit, the gas valve fails. If that's the problem, replace the thermocouple.

1. Shut off the gas valve on the water heater and the gas valve on the line near the heater. Remove outer and inner doors, and loosen the pilot and supply tubes and the thermocouple connections to remove the burner assembly.
2. Step 2 Loosen the screw holding the thermocouple to the bracket. Remove old thermocouple. Bring it with you to the store to ensure you are buying the proper replacement.
   
3. Step 3 Install the new thermocouple. Position the thermocouple so that the pilot flame heats 1/2 inch of the tip.
   
4. Step 4 Reinstall burner assembly in the water heater. Tighten burner supply tube, pilot tube and thermocouple connections. Tighten thermocouple no more than a quarter turn more than hand-tight.
   
5. Step 5 Turn on both gas valves. Check supply tube and pilot tube for leaks with soapy water. If soap bubbles, tighten connections to fix leak. Ignite the pilot light, and make sure the thermocouple tip is heating up. Replace inner and outer doors.