I have a All-Pro 115,000 btu multi fuel heater. When first plugged in fan runs, fuel sprays out the nozzle but heater won't fire. Any suggestions?

The fuel/air mixture is not right.

• Start by setting the pump pressure to factory specs.
• Stop all air/vacuum leaks between the air pump & nozzle
  
• If the problem persists, replace the nozzle. Desa recommended annual replacement. Simply stated- the nozzle wears out to a point that the fuel is a spray rather than a fog and the fuel can't burn completely.
  
• You don't state the type being burned. Diesel smells more than kerosene.
  

Take the top cover off of the unit. Plug it in and look inside the burner can to see if the ignitor is glowing. If not you probably need an ignitor. You can remove it to check the heating element to see if it is intact, but be very careful, it is more fragile than glass. If it is intact, you may have a control board issue. The ignitor should glow before the fan starts. Be careful to stay away from the fan blades while doing this. If the ignitor glows, and the motor starts, you should then be able to see fuel spraying out of the spray nozzle. You may need a flash light. If the fuel does not spray out of the nozzle in the correct amount, the unit will shut down. There is a photo cell that detects ignition. If the fuel pattern does not look even, you could have low air pressure out of the pump, a dirty fuel nozzle, or a plugged fuel screen inside of the tank. The air pressure comes from a pump on the back side of the blower motor. Insure that the filter are clean on the pump; there are three of them, and the plastic end cap needs to come off to access them. If they are dirty, they need to be replaced. The air pressure off of this pump is very critical to proper fuel delivery. The rated output pressure of the pump is on the heater data plate. You will need a low pressure air gage to check this pressure. Another source of low air pressure is the plastic end cover over the filters. They tend to crack with age. Spray soapy water on the end cap while the blower is running to look for leaks.

Does the blower motor start when you plug it in/turn it on? It may take around 5 seconds if your heater has a HSI(hot surface igniter). If it does you need to check the igniter and the fuel flow. Either way, remove the top of the heater. You will be able to see the fan, igniter, and fuel nozzle. Turn the fan by hand to see if it turns freely. If it does, watch out for the fan and turn the heater on. Look for the igniter to start sparking (spark plug type) or glowing (HSI type). Next, use a flashlight to look for fuel spraying from the nozzle. If fuel isn't spraying, try cleaning the fuel nozzle and check the fuel filter. Watch out for the HSI, if you have one, they are very brittle and easily broken. If you still don't have fuel flow after cleaning the nozzle and the fuel filter, you may have an air pressure problem. Let me know and I will tell you how to check it. Don't forget to rate the answer if it works.

Well it is getting fuel but is it atomized in very small droplet form? If so is your igniter close enough to ignite the fuel? You see these spray a very fine conical mist under high pressure, if the mist is not defined or conical it sprays past the igniter. If it is fine and cone shaped it could be the positioning of your igniter. Please check both by removing the top section of the heater and watch what is going on in there. My thoughts are a bad nozzle and if you replace it pay attention to spray angle and GPH rating printed on the side of the nozzle.

Could be a dirty air filter. Fuel nozzle could be clogged. Fuel filter clogged, if it has one. Some don't. Could be a problem with the low pressure compressor that is attached to back of the fan motor.

Get online to www.desatech.com You and download a manual there.
There are two ports on the black box behind the fan motor. One is just a plug where you should connect a pressure guage. The other is like a relief valve that keeps the pressure in the black box constant. The air goes to the fitting behind the fuel nozzle. This fitting is an eductor. The air flowing through it creates a low pressure which then draws the fuel to the nozzle. The air pressure and therefore the amount of airflow controls how much full will be drawn in. More pressure, more fuel. Less pressure, less full. To lower the pressure, back the screw out that has the hole in the center.

flame sensor clean with steel wool usually right next to hsi should fix.

A heater with this problem is probably the hardest to determine the cause. There is no carb orn thermostat to adj. If it uses a spark plug ignitor I would check the plug gap and make sure it is at an angle to the nozzle. If it has Hot Surface Ignition this will not be the problem. I would then check the fuel filter in the dip tube in the tank and the pump pressure. I should be about 4.5 psi. I would also remove the nozzle and replace it or at least blow it out backwards withlcompressed air to clean it. If all these items fail to correct the problem I would replace the flame sensor. Let me know what you find out or if you have any questions.

check out the fuses getting blown out on the internal chip circuit board and also the overheating component on that same circuit boasd.the burnt component will look little bit extra blackish on its sides.

sound like there is dirt and stuff in the fuel tank.when the heater fires up it pulls this stuff up into the filter.as it runs it plugs the filter off causing the heater to shut off.whe it shuts off the garbage falls back into the tank.when you refire the heater it pulls the garbage back up again.it never pulls it up the same so the time verys every time