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The cause depends on the fuel, and each one has a single dominant culprit. On a gas grill, a grill that lights but stalls around 250°F to 300°F has almost always tripped the excess-flow safety device in the propane tank valve, and a two-minute regulator reset fixes it. On charcoal, it is nearly always too little fuel or blocked airflow. On a pellet grill, it is damp pellets or an ash-choked firepot. Work through your fuel below, in order.
The 60-second triage
| Symptom | Most likely cause | Fix |
|---|---|---|
| Gas grill lights but caps at 250–300°F | Tripped regulator (excess-flow device) | Regulator reset — see below |
| Gas grill: low, lazy yellow flames | Blocked burner ports or a spider web in a venturi | Clean burner tubes and venturis |
| Gas grill: one burner weak, others fine | That burner tube is corroded or clogged | Clean or replace the tube |
| Charcoal never gets past medium | Too little fuel, or vents closed | Full chimney; both vents fully open |
| Charcoal starts hot then fades fast | Ash blocking the bottom vent | Clear ash before every cook |
| Charcoal will not light properly | Damp or old briquettes | Fresh fuel, stored sealed and dry |
| Pellet grill stalls below set temp | Damp pellets or ash in the firepot | Fresh pellets; vacuum the firepot |
| Pellet grill swings wildly | Cold weather, wind, or a dirty temperature probe | Wipe the probe; shelter or insulate the grill |
| Any grill, temperature down ~100°F | Wind, cold, or the lid left open | Move out of the wind, preheat longer, lid down |
Gas: the regulator reset, and what comes after it
Every propane tank valve contains an excess-flow safety device, designed to shut the gas down to a trickle if it detects a sudden surge — the signature of a severed hose. It cannot tell the difference between a severed hose and a valve opened fast with the burners already turned on, so it trips constantly on grills that are perfectly healthy. The result is a grill that lights, holds a small flame, and refuses to go past roughly 250°F to 300°F.
The reset:
- Turn every burner knob to off.
- Close the propane tank valve fully.
- Disconnect the regulator from the tank.
- Wait a full 60 seconds — this is the step people rush, and it is what lets the device re-seat.
- Reconnect the regulator, hand-tight.
- Open the tank valve slowly, a quarter turn at a time, with all burners still off.
- Now light the first burner, then the others.
Do that every time you connect a tank and it will rarely trip again. Our gas-specific troubleshooting page covers the follow-on checks in more depth.
If the reset does not fix it, work down this list. Low fuel is easy to rule out — weigh the tank or run warm water down the side and feel for the cold line where the liquid level sits; see telling if a propane tank is empty. Blocked burner ports show as flames on only part of the tube: brush them clear with a stiff brush and clear each port with a paperclip, never a toothpick that can break off. Spider webs in the venturi tubes are a real and famous cause — small spiders are attracted to the odorant in propane and build nests in the tubes, which starves the burner and can push flame back toward the valves. Corroded burner tubes are the end-of-life failure; they are a $40 part on most grills and a twenty-minute job, covered in replacing gas grill burners.
Charcoal: it is almost always fuel quantity or airflow
Not enough charcoal. The most common cause by a distance. A 22-inch kettle needs a full chimney — roughly 80 to 100 briquettes — for high-heat direct cooking. Half a chimney gives you a medium fire that feels disappointing on a steak. For two-zone cooking you still light a full chimney and bank it to one side rather than spreading a thin layer everywhere.
Airflow. A charcoal fire is a fire you control with air. Both vents wide open is maximum heat; closing the bottom vent chokes it. The failure people miss is the bottom vent silently blocked by accumulated ash, which is why a grill that ran fine last month fades this month. Clear ash before every cook.
Wet or old fuel. Briquettes absorb humidity from a damp garage and never recover. They light reluctantly, smoke, and never reach temperature. Store bags sealed in a bin.
Not enough time. Coals need 15 to 20 minutes after being dumped from the chimney before the grate is genuinely at cooking temperature, and the grate itself needs to preheat. Our how long to let charcoal burn and temperature control guides cover this properly.
Pellet: damp fuel, dirty firepot, cold air
Damp pellets. Wood pellets are compressed sawdust held together by lignin. Humidity makes them swell and crumble, and crumbled pellets burn poorly, jam augers and choke firepots. If the hopper has sat through a wet week, empty it and start again with pellets from a sealed bucket.
Ash in the firepot. Ash accumulates around the igniter and smothers combustion. Vacuum the firepot every few cooks with a shop vac once the grill is stone cold — this is the single most effective pellet-grill maintenance task and the one most owners skip.
A dirty temperature probe. The internal probe is a small metal pin in the cook chamber, and a coating of grease insulates it. The controller then reads a temperature the grill is not at, and either overshoots or stalls. Wipe it whenever you clean the grates.
Cold weather. An uninsulated single-wall pellet grill below freezing may not reach its top temperature at all, and will burn far more fuel trying. Insulated blankets exist for most models and make a large difference. See our pellet grill picks for which models are double-walled.
The causes that apply to every grill
Wind. The most underestimated factor in outdoor cooking. Moving air strips heat from the cook chamber and the food, and a grill in an exposed corner can run 100°F cooler than the same grill six feet away behind a wall. Flat-top griddles suffer worst because there is no lid at all.
Cold ambient air. Everything is slower and hungrier in winter. Add 5 to 10 minutes to preheat and expect higher fuel consumption; a propane tank chilled well below freezing also delivers lower vapor pressure, so gas flow itself drops.
Cooking with the lid open. A grill is an oven. Open, it can only heat by radiation from below; closed, it circulates hot air around the food. If you have been searing everything with the lid up and wondering why chicken takes forever, that is the answer.
Grease and carbon buildup. A heavy layer of carbon on the grates and heat deflectors insulates them and blocks flame paths. See how to clean a gas grill and our grill brush picks — and note that if you use a wire brush, the grate must be inspected for shed bristles before every cook.
A lying lid thermometer. Built-in dome thermometers are frequently 25°F to 50°F off, and they read the air at the top of the dome rather than at the grate. Before assuming your grill is cold, check with a separate thermometer at grate level.
When to stop and get help
Stop and shut the fuel off if you smell gas that does not disperse, see flame anywhere outside the burner tubes, see flames at the hose or regulator, or find the hose cracked, hardened or scorched. Those are leak and burn-back conditions rather than heat problems, and they get worse. Check for leaks with soapy water brushed on the hose and connections — bubbles mean a leak — and never with a flame. Replace a suspect hose and regulator assembly rather than repairing it.
And whatever the fault: never move a grill into a garage, a carport, a covered porch or any enclosed space to troubleshoot it, and never light one there. Charcoal, propane and wood pellets all produce carbon monoxide, which the CPSC describes as colorless and odorless — no smell, no warning. Charcoal is especially dangerous because a bed of coals keeps producing it long after cooking ends. See is it safe to grill in the garage.
A cool grill is a food-safety problem too
A grill running well below its indicated temperature means food takes far longer than the recipe says, and the temptation is to judge doneness by appearance instead. Do not. USDA FSIS sets safe minimum internal temperatures at 165°F for all poultry, 160°F for ground meats, and 145°F with a three-minute rest for whole cuts of beef, pork, veal and lamb, and states plainly that the only reliable way to know food is safe is a food thermometer in the thickest part, away from bone and fat. Time and color are not checks — see our meat thermometer picks. If a cook has stalled and the food has been sitting in the 40°F to 140°F range for more than two hours, do not try to save it.
More from this hub: outdoor living & grills · gas grill not getting hot · charcoal grill will not stay lit · grill BTUs explained · how we rank.