Yellow Flame on a Gas Grill

Gas burns cleanly when it's mixed with the right amount of air before it reaches the burner ports. That mixing happens in the venturi, the open tube at the front of each burner that slides over the gas valve. Gas shoots out of a small orifice into the tube, pulls air in with it through the air shutter openings, and the mix travels down the burner to the ports.

A properly mixed flame is blue, crisp and fairly short. When there isn't enough air, the gas doesn't burn completely. The flame turns yellow or orange, grows taller, wavers, and gives off soot. Incomplete combustion also produces more carbon monoxide, which is one reason grills belong outdoors in open air.

Spiders and insects in the venturi

Spiders are drawn to the smell of propane and natural gas odorant and like the shelter of a burner tube. Webs and egg sacs narrow the tube and choke off air. In Southern California, where grills often sit for a few weeks between uses, this is the cause we find most often. Our guide to spiders in burner tubes covers prevention.

Burner not seated on the orifice

If a burner was pulled for cleaning and put back slightly off, the gas jet won't be centered in the venturi. You get poor mixing and sometimes gas escaping around the outside of the tube, which is dangerous.

Air shutter closed down

Some grills have an adjustable air shutter at the burner inlet. If it was knocked closed or set wrong, the flame goes yellow. Many modern grills have fixed shutters, so check your manual before looking for one.

Grease and debris on or in the burner

Heavy grease buildup on the burner or blocked ports changes how the flame burns. A thorough cleaning usually fixes this.

Wrong orifice for the gas

A grill set up for natural gas but running on propane (or a botched conversion) can produce huge yellow flames. Propane is supplied at higher pressure and carries more energy per unit, so it needs smaller orifices. This is a safety issue and calls for a proper gas conversion, never improvised fittings.

When clean tubes and properly seated burners don't fix it, the problem is usually in the gas side: an orifice that's damaged or incorrect, a regulator that isn't supplying the right pressure, or a grill that was converted without the right parts. Those need a tech with the correct parts and, on natural gas, a pressure check. A yellow flame that comes with low heat often shares a cause with the problems in why your grill won't get hot.

It's also worth looking at the burners themselves. Corroded ports that have grown into slots throw large, uneven flames that look yellow and ragged. That's covered in signs your burners need replacing.