When heater starts it does not always light, I get a C3 code

It sounds like you are using a natural gas fired heater and your fuel is propane. If this is the case, you need to buy a propane conversion kit.

Check noggle for dirt, check fuel filter for dirt. Check al rubber hoses for leaks, Set air pressure All these will cause it not fire.

pull the vacuum line from the regulator and turn the key on and see if gas drips or sprays out from the nipple on the regulator if so that's your problem the fuel is going threw the line into the intake port

That condition is a fire hazard condition, I recommend towing to a good mechanic, as any errors increase fire hazard.

What needs to happen is to locate EXACTLY where the fuel is coming from, then why. Sometimes seals, sometimes stuck injector, sometimes computer invoking based on something.

I would expect that you have a check engine light on, if you do not, that may point you to external leaks only, and not leaking injectors, but check everywhere to that point. Fuel leaves stains, so it should be easy to find. No smoking, and use LED lights and lower explosion and/or fire possibility.

If you do have check engine light, pull the codes and follow from there, but remember, a leaking injector may manifest as oxygen sensor issue, when raw fuel on it is the issue, sensor a victum. the codes are a clue, not the answer.

clean the spark plug,check the sensor for ignition.Water in fuel?
This will be a good start

I am not to sure of the trouble codes on Mr.Heater but this is usually a fuel related problem. My routine maintenance is remove top half of heater and clean fuel system from nozzle back to the tank.Remove nozzle,clean the screen behind the nozzle they corrode over the summer sometimes inspect the nozzle for corrosion or damage. Inspect lines back to pump then to filter. The filter can be cleaned out with compressed air and a blow gun blowing air thru the filter backwards. Now check the fuel line to the tank and make sure it is submerged in the fuel. Before putting the top on locate the fire sensor and give it a quick cleaning with windex and soft terry cloth rag. Put your heater back together and check air filter to pump clean it and fire away. This works 90 percent of the time. Good luck!

The white smoke is the kerosene fuel hitting the hot combustion chamber. Your flame has went out. The cause for this could be many. The first thing you need to do is check your fuel. Remove your fuel cap and look at the bottom of the tank for trash or water. Use a good flash light. It will all settle to the bottom. If so, drain and clean out your tank. Add fresh kerosene. Check your fuel filter. Replace if dirty. Test again. If problem continues, It is possible that your photo eye could be deffective or just dirty. It is located next to the ignitor or spark plug. It sees the flame. If the flame goes out, the unit shuts down. The flame has to be smooth (not sputtering). Water in the fuel will make it sputter and the unit will shut down. When the water/moisture in tank settles to the bottom, your suction fuel line is just off the bottom which results in it picking up the water instead of good fuel. Always disgard the old fuel from previous year and start with fresh fuel. This will cut down alot of your problems in the future.

Hi you will have to clean it all out till you get all the stuff ou tof it it has pulled all this through from being run dry , you not far off just more to do

Light the panel at a very low pressure The panel not lighting is probabably the first pael to get gas and is not having the correct air /fuel ratio to burn. Make sure the igniror is properly positioned. The lit panel can ignite the raw gas expelled by the unlit and create a flash ignition . (explosion) The ceramics a very delicate and I would be reluctantant to advise on clean. You can blow it out with compressed air if available..

Try a new CAD falme sensor, or high limit control, both very cheap.