Gas safety — read this first
Stop and deal with this first
If you can smell gas, or the flames are yellow and lazy rather than blue, do not carry on cooking. Turn the cylinder valve off, do not operate anything electrical near it, and move away. Yellow flames with a smell of gas point at an obstructed burner rather than a leaking joint, and both need the appliance checked before it is lit again.
The gas grill heats unevenly
Food on one part of the grate cooks noticeably faster than the same food elsewhere, so a single batch finishes at several different times.
Work out which one it is
Each cause below lists the signs that point at it rather than at the others. Start with the signs, not with the fix.
Burner tube ports are dirty or blocked and are restricting gas flow.
commonSigns it is this one
- The cold area is consistently in the same place across different cooks.
- With the lid up and burners lit, the flame is erratic or does not run the whole length of the burner tube.
- The flame stays low even with the control knob at its highest setting.
Why it happens: A gas burner distributes heat through evenly spaced ports running the length of the burner tube. Weber states that these foul with repeated use and that blocked ports restrict full gas flow, giving three signs: the grill does not reach the desired temperature, it heats unevenly, and one or more burners do not ignite. The flame pattern reproduces the blockage and the grate above reproduces the flame.
What to do
- Follow the manufacturer's cleaning procedure for the burner tube ports, with the gas off, the cylinder disconnected and the cooker cold. — next time, reliable
Weber's manual is explicit that ports are cleaned and never enlarged: do not enlarge the valve orifice or burner ports when cleaning. Burner geometry and cleaning method vary by model, and this is the one area where the maker is the authority.
Next time
- Clean burners on the maker's schedule rather than when a problem appears — Weber asks for the burner tubes and the spider screens to be inspected at least once a year.
An insect nest in the burner's venturi is choking the air and gas mixture.
occasionalSigns it is this one
- The flames are yellow and lazy rather than blue with occasionally flickering yellow tips.
- There is a smell of gas at the same time as the yellow flames, which distinguishes this from ordinary port fouling.
- The barbecue has been stored or unused for a season.
Why it happens: The combustion air openings of the burner tubes carry stainless screens precisely because spiders and insects nest in the venturi section behind them. Weber states that such a nest obstructs normal gas flow and can push gas back out of the air opening, so the burner runs on a wrong mixture and burns yellow and lazy rather than blue. The hazard is not uneven cooking but a fire in and around the gas valve.
What to do
- Stop using the barbecue and inspect and clean the spider and insect screens before lighting it again, following the manufacturer's procedure with the gas off and the cylinder disconnected. — after cook, reliable
Weber's instruction is to contact customer service if a screen is damaged or cannot be cleaned, rather than to run the appliance without one.
Next time
- Inspect the spider and insect screens at least annually and specifically after a period of storage or non-use.
It is not a fault: the cooker has zones and they are doing their job.
commonSigns it is this one
- The variation follows the burner layout, and disappears when all burners are set the same.
- The difference is between the middle and the edges rather than a dead patch.
Why it happens: A multi-burner grill is designed so that burners can be run independently, which necessarily makes the grate uneven. Edges also lose heat faster than the middle on any cooker.
What to do
- Use the variation deliberately: cook over the hot zone and park over the cooler one. — during cook, reliable