Gas oven lights pilot straight away but takes a long time for main burner to work has it got a thermocouple and cuold this be at fault

The thermostat shuts off the main burner.The pilot light gas is controlled by the thermocouple which the side of the pilot flame has to envelop. If the flame is too small or too far away from the flame, it shuts the gas off to the pilot. The thermocouple generates a small voltage which keeps the pilot gas open. It can over time fail itself, so look at replacing it. The thermostat sounds like it's failing too.

Sounds like the pilot is mounted to far away from the burner. I have seen it happen before where the pilot has detached and the main burner will just keep pumping gas in until it hits the pilot flame and just flash flames and everything goes out.

Or it just could be a bad thermocouple that is going out all the time.

Probably the safety valve. This unit broils and bakes off the same gas burner. A spark ignitor lights the pilot and this save gas because no standing pilot is needed. It takes a few minutes for the thermocouple bimetal combo to release the gas. When the temp gets to the desired rate then the bulb on the oven control closes off the flow of gas. To recap: The flow of gas comes from a regulator along a rail which supplys the gas to the top burners and the oven control. older models had pilot light tubing going down to the oven and to the top burners. This newer style uses a spark module to light off the top burners and the oven. So when yall turn the the oven on the spark ignitor lights the pilot first and then after the mercury bulf thermocouple heats up the bimetal inside the valve opens allowing gas to flow out to the pilot and ignite the gas burner. the temp rises and the mercury bulb oven control expands closing off the flow but not the gas safety valve. I would suspect the safety valve on this one.

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Hi


Thanks for using FixYa. From what you have described it seems that possible oven control is not sending gas for the pilot light. The pilot light works but no main burner ignition - possible pilot assembly is dirty and the pilot flame is too small, safety valve and thermocouple is faulty, the bulb from the safety valve is out of position and the pilot flame is not touching the thermocouple bulb. Some ranges use a standing pilot light ( small flame is on all the time ) while others use an spark ignition to light the pilot light flame and the pilot light flame heats up the thermocouple bulb to allow the main gas to flow through the oven burner.


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Thanks
Rylee

Hi

If it won’t fire then it is possible that the oven control is not sending gas for the pilot light. The pilot light works but no main burner ignition - possible pilot assembly is dirty and the pilot flame is too small, safety valve and thermocouple is faulty, the bulb from the safety valve is out of position and the pilot flame is not touching the thermocouple bulb. Some ranges use a standing pilot light ( small flame is on all the time ) while others use an spark ignition to light the pilot light flame and the pilot light flame heats up the thermocouple bulb to allow the main gas to flow through the oven burner.
The flame needs to heat the bulb up enough to tell it to open the gas valve. Several things can go wrong here that keep this from happening:
The pilot flame may not be hot enough, usually because the flame is yellow instead of pure blue or is too small. The cause for this is usually a dirty pilot assembly. The pilot assembly would either need to be cleaned or replaced.
The thermocouple bulb may not be positioned properly in the flame. You can't heat the bulb properly if it's not in the pilot flame! The thermocouple bulb needs to be in the upper third of a pure blue pilot flame--that's the hottest part of the flame.
The thermocouple itself may be burned out. It happens. It's an internal part of the gas valve so, no, you can't just change the thermocouple bulb separate from the gas valve.
But when you turn on the oven or the thermostat calls for heat, the pilot flame gets bigger and jumps down so it can heat up the thermocouple bulb. This extra gas to increase the pilot flame size comes from the thermostat.
If the pilot flame jumps upwards or just gets bigger, but doesn't shoot down, then you need to replace the pilot assembly.
If the pilot flame size does not increase or jump down when turning on the oven thermostat, then the problem is the thermostat not sending enough gas to the pilot assembly. It's also possible that the pilot gas supply tube has a hole in it somewhere.
One final point on the spark-assisted pilot ignition systems. The spark comes from the spark module--the same module that sends spark to your surface burners to light them up. If you're not getting a spark when you turn the oven on, then there are several possibilities:
There could be a problem with the switch in the thermostat. You can confirm this by doing a simple continuity test of the thermostat contacts. If you don't read zero ohms when you turn the switch on, replace the thermostat.
The spark module could be bad. You'll need to measure the voltage at the oven terminals of the spark module when you turn on the oven. If you get 120v but no spark, it's probably a bad spark module. Replace it.
Could be a bad spark wire or broken electrode.

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Thanks
Rylee

the pilot light is there for 2 purposes. number 1 to light the burner and number 2 to heat up the thermocouple, thermocouple is a wire that the flame from pilot suppose to surround by fire. if the pilot is to low it will not reach the thermocouple. you can take the gas line that supplies gas to the pilot and clean it with a safety pin or a small needle. you can test the thermocouple by heating it up with a blow torch on low heat, get it red hot and then turned on the oven. if the oven works clean the pilot, if the oven do not work, replace the thermocouple if separate from safety valve. if thermocouple is part of it replace the safety valve.

The declining pilot light might be an indication it is being starved of oxygen by the main burners or some other sort of circumstance.

I have noticed how in a closed room without ventilation the pilot light soon begins to decline and then springs back again when a window or door is opened while the main burners are hardly affected.

This is the gas equivalent of sending canaries down coal mines and is an essential safety feature. If the pilot light declines very much the thermocouple bulb will not be heated and the gas supply to the main burners will be cut off. This is why the pilot light is set at an angle and the thermocouple bulb is slightly offset.

I am not sure if this helps but I hope it does.