The gas seems to have restricted flow from the heater so therefore is not igniting. The bayonet seems fine to the heater but the gas is not staying on am thinking maybe a blockage somewhere. Thanks

Hi,

Please be careful when dealing with products using gas. Double check that the area around where ignition occurs does not have air blocked off as low oxygen would stop fire from occurring. You can also check fuel level of machine. Thank you.

If your heater is gas, must have at least one igniter electric or thermo couple, also a flame sensor could be present, the thermocouple send a milivolts signal to the gas valve this signal is initiated by the heat provided to that part, practically the igniter, thermocouple, and or thermo pilot "talk" to the gas valve, hey, we have flame in here you can open and let the gas flow, if there is a flame sensor this one would say, hey, there is a good flame at the burner stay open until the control thermostat tell you to shut down, I would change the pilot assembly if your unit is gas, because sometimes the pilot opening gets restricted and the flame is too small but strong enough to activate the gas valve, when the burners kick in shut down the pilot, and remain lit, in the next cycle pilot is out.

Usually a thermocouple or similar device is employed to allow fuel to flow once the unit sees that there is sufficient heat to ignite the fuel. Otherwise it can be a fuel valve that "sees" an unusual flow of gas which sets off the safety.

The capacitor in that unit is for starting the motor that drives the blower fan. It has no impact on the ignition of the gas burner. On the control board, there is a light that should be flashing, can you tell us how many times it is flashing?

Your thermopile that tells the heater how hot the water is has failed. It should kill the heat at a temperature of 104f. This also indicates that the limits are not doing their job, as they should be killing the heat at 135f (low limit) or 150f (high limit). Schedule 40 pvc is rated at about 140f.
This many failures at once is rare, and typically indicates that the heater has been rigged. Get a tech out to fix it correctly. You are literally playing with fire.

flame sensor, air flow restriction or blower not producing enough pressure. clean the flame sensor to start. inspect venting, etc

There is a flow switch if that's not working. same problem needs to be tested Gas valve solinoid could cause this Igniter could cause this problem Gas pressure regulator wrong pressure should be about 2.7KPA LPG Gas valve should be set to about 2.6 KPA LPG

check the silver line going to the pilot might be restricted with spider web if no spider web need new pilot generator

Never drill or try to make the pilot hole larger, this will cause a large flame that cannot be controlled. Check the main parts, first see if you have a spark, next check for leaks, to see how to do a leakage test see patio heater problem solving page. If no leak try changing the thermocouple, these will wear out and can last up to 6 years. Also check the electromagnetic valve that sits inside the gas control valve and if fitted check the tilt switch works. The tilt switch can be shorted out to see if it works.

When you say "it won't stay on at all." Do you mean the burner and the pilot flame shut off together or does the pilot remain lit? Is the unit showing any Fault Codes on the LCD display?