You shouldn't encounter a lot of problems burning with a fire pit. It creates an efficient cycle of fire, fuel, and oxygen; as long as those three requirements are met, the fire pit should operate without any problems. If you do experience problems getting your fire pit to burn, you may want to look into some of the following issues.
1. Air Intake
To work correctly, the fire pit must have a constant supply of air. If the air holes or air intake vent have been plugged, or don't exist at all, you may have a hard time getting a fire to burn. Use a nail to clean out holes and air intake openings. To test the air flow, leave the loading door open and check whether the fire burns more brightly.
2. Bottom Full of Ashes
If the bottom of the fire pit fills up with burnt ashes, it may not receive enough oxygen to burn, even if the air intake holes are clean and open. After each use, empty the ashes when the fire pit cools down. This habit should prevent the problem and also increase the period of time your fire pit will last by reducing decay from rust.
3. Solid Cover
A solid fire pit cover will not allow the smoke to escape the fire pit and will effectively suffocate the fire. You should only use a solid cover when you are ready to extinguish the fire. A spark screen should be made from a heavy-gauge wire mesh, not a solid material.
4. Damp Fuel
If you use damp wood or charcoal, you will struggle to light the fire, even if you apply copious amounts of lighter fluid. If no dry fire fuel is available, you may want to wait until another time. Alternatively, you can buy special waterproof fire starter logs, some of them made from synthetic materials and others from the heart of pine trees (commonly known as fat lighter).
Other things that could go wrong include doors that won't open or spark screens that do not seem to fit properly. Both of these problems point to one of two possible causes. Either a piece of wood or some other material is jamming the door or screen in place; or the fire bit is not sitting level, and the stress of its position puts an unnecessary bind on the few movable parts.
If addressing these causes does not fix the problem, check for missing screws, broken hinges, or dents that affect how well that part is able to move. Replace broken hinges. Straighten dents or bends by tapping a piece of wood against the bend with a hammer. Do not hit the dent directly but use a block of wood that will cushion the blow and distribute the force of the impact over a larger area.