No flow of gas to fire after pilot light is lit and turned on.

no info generic answer --check thermocouple --and safety switches

The system I am familiar with uses a vapour pressure type thermocouple and if the pilot remains lit the thermocouple is working as it controls the gas for the pilot and the burner at the same time from the same source - if the gas control is ok and the flow isn't prevented by the thermostat then if the pilot remains alight, there should be a flow of gas and the burner should light - unless the gas jet is blocked or something else, some other type of blockage is preventing the flow of gas to the burner...

I suggest you check the gas jet and the flow of gas to it...

First locate where to light pilot. You can do this by following thin aluminum colored tubing from control valve to inside heater.In general on top of your gas control valve is a knob. Turn indicator of this knob to pilot and depress knob. This will start gas flow to pilot at end of thin tube. Hold this knob in the depressed position and light pilot. DO NOT release knob for 30 -45 seconds. Then release knob and pilot will remain lit. Then turn knob to on position. If pilot will not stay lit you may need a new thermo coupler, which senses heat from flame to keep pilot gas flow open.
Good luck

Pilot needs cleaning out , try blowing it out with a can of air or blowing it out with tube

If your pilot light is lit, then you do have some gas flow, so it is probably the thermocoupler (the part heated by the pilot light) that is not telling the gas valve to open the main line. Sometimes it is just a case of residue on the thermocoupler that is not letting it get up to temperature and sometimes it has been knocked out of alignment and the pilot light is not putting direct heat on it.

A cleaning with steel wool (don't overdo it) would take care of the residue, and you can GENTLY move the thermocoupler back over the pilot flame. If neither of that helps then replace the thermocoupler.

Dave, make sure that the gas valve on the Propane tank, is fully open and that the inline gas shutoff valve near the heater is turned ON. Those are the basic two things that would prevent the gas from flowing thru the gas line, to the heater.

If the above valves are ON, the problem then lies with the gas control valve on the water heater. If it has pilot light that has to be lit, make sure that the heater's gas control valve is properly in the PILOT Position, before attempting to light it. It must be able to be pushed ALL the way in and you should feel strong pressure pushing back at you (other than spring pressure). When you feel that, it's in the PILOT Position and ready to be lit. Once it's lit, continue to hold the Pilot Button in for 1 minute, then release it. If the Pilot stays lit, turn it to the ON Position.

Hope this helped you to troubleshoot and solve the problem. Please let me know. Thanks.

model lg250p 2 fill tanks no gas at pilot light does this work off flow of water; for power, to control gas flow, unit in good condtion

if pilot is blue and torch like then the thermocouple is bad. if pilot is layz and yellow then it needs to be cleaned.remove pilot gas tube and clear orifice,looks like small thimble. reassemble and check tightness with soapy water when gas is flowing

If the pilot flame is weak, when the main burner is ignited, there can be enough 'whoosh' of air and gas to blow out the pilot. There may be a little of grit in the pilot valve jet hole restricting the flow, hence the weak flame. Try using a piece of fine wire to clear the obstruction. If that does not help the pilot jet will have to be unscrewed and cleaned with compressed air. Ensure the gas is turned off before attempting any maintenance.

Make sure thermostat is set higher than water temperature. Make sure pump is running and water is flowing through unit. If gas valve is not opening then flame sensor or gas valve is bad.