PILOT LIGHTING BUT CANNOT TURN ON WITOUT IT GOING OUT

It could be that the gap for the igniter is too big Try lighting it manually There should not be that much air in the line .

Assuming it is not an electric spark, but is really the type with a real pilot light:
Move the gas control on the water heater to PILOT
Push the valve handle on the gas controller down to start the gas flowing to the pilot.
Using a match, light the gas at the pilot while holding the gas controller valve handle down.
Keep the gas valve handle depressed for 30 seconds after lighting.
Release the gas controller vale handle - the pilot should remain lit. If not, repeat lighting one more time
Once the pilot remains lit, turn the gas controller valve to On - this should cause the main flame to come on.

NOTE: DO NOT LIGHT A MATCH IF YOU SMELL A HEAVY CONCENTRATION OF GAS - CALL A SERVICEMAN AND VACATE THE AREA

pilot light keeps going out! more then likely its the thermal coupling doing this. if bad it shut all gas to heater for a safety measure. just shut power off, then turn gas off and replace it. then you should be ready to go. to relight heater hold down on gas vavle knob in the pilot position, hold down and light it at the coupling where gas comes out. when it is lit, continue to hold down for 60 seconds. release knob very slow. then if its lit, turn to the run position. if flme goes out, wait at least 5 minutes to expel the gas fumes and turn to pilot and try again. good-day !

General causes for pilot going out: downward draft of air from outdoors, back-venting of furnace into water heater vent, bad thermocouple, or burner parts need cleaning, or bad gas control valve, or air in gas line.
Water heater in attic: hot attic conditions stop natural flow of vent gas upward.
Open following link for troubleshoot resources and cleaning illustrations and instructions:
http://waterheatertimer.org/How-to-install-gas-water-heater.html#troubleshoot
http://waterheatertimer.org/pdf/Pilot-light-will-not-stay-lit.pdf
Check venting by lighting a match under the vent hood and see if smoke drafts immediately upward.

check and or replace the thermal coupling. the coupling goes into the main gas control, if the coupling is bad it will shut off gas supply. as a safety measure.

Sounds like it is your thermal coupler. Check for a replacement part at your local hardware store. Good Luck.

Either the pilot light orfice is dirty, and you will need to pull it out and clean it, or the thermocouple is bad. If the pilot goes out as soon as you let the button go then it is most likely the thermocouple. If the pilot stays lit for a few days or hours then you will need to clean the pilot orfice, heres how:
1 turn off the gas supply
2 unhook the main burner gas line from the thermostat, this is the line that goes to the burner
3 unhook the pilot supply line it is usually next to the main burner line
4 unhook the thermocouple from the thermostat
5 remove the burner assembly
6 take the orfice out of the pilot line and clean it out by blowing thru it, use an air compressor if needed.
7 reassemble and light pilot

1) Open the door on the bottom of the tank to show the burner. 2) Turn the valve to "pilot" and depress. 3) Light the match, (best if you have a candle/grill lighter), and follow the skinny copper tube from the valve to the burner inside (this is called the thermocoupler). At the end of it, you will see the pilot. 4) Once pilot is lit, keep valve depressed for a minute (this warms the thermocoupler, thus sending a signal to the valve saying the pilot is lit). 5) Let go of the pilot button (usually red). 6) If pilot stays on, put the door(s) back on and turn the valve to "on". You will hear/see the gas ignite when complete. Good luck!

YOUR WATER HEATER HAS WHAT IS CALLED A STANDING PILOT-STAYS LIT ALWAYS WHEN THE PILOT GOES OUT YOU LOOSE EVERYTHING. YOU HAVE TO REPLACE THE THERMOCOUPLE WHICH KEEP THE PILOT LIT. ONCE THE PILOT IS LIT THE THERMOCOUPLE SENDS IN MILLIVOLTS TO THE BURNER TO SAY ITS READY FOR BURNING
IF YOU ARE NOT FAMILURE WITH THIS REPLACEMENT PLEASE FIND SOME ONE WHO CAN. IT IS NOT HARD TO DO ASK A NABOR OR FRIENDS SOME HAS TO KNOW HOW. SERVICE COMPANYS ARE OUT FOR THE MONEY FOR A 10 MINUTE JOB

Try this, turn the black gas ****, on top of the control box, to the Pilot position. Set the temp. control on the front of the box to the desired temp. Then, hold a match or whatever else you use to light it, next to the end of the pilot, then, while holding the match to the pilot, press the reset button on top. When the pilot lights, continue to hold the reset button down for about 1 minute. Then, after a minute, turn the gas **** to the ON position, then it should remain on.