Flame on gas grill is too small

From: http://bbq.about.com/cs/replacementparts/a/aa071100a_3.htm

Symptoms and Solutions Low Flame: The grill just doesn't want to heat up. This can be cause by several things. Taking it from the fuel source to the flame, lets start with the burner. Newer propane tanks contain a self regulating feature that will automatically slow down the flow of fuel if it thinks it's too high. This can be solved by turning the tank valve off completely and disconnecting it. Open the control valves (on the grill control panel) and ten close them. Reconnect the fuel tank and slowly turn on the valve. Now light the grill to see if that fixes it. Otherwise check the control valve(s) and venturi tubes for obstruction and alignment. Make sure that the flow of fuel is continuous. Check the burner for clogged gas holes. You can usually see this problem by observing how the grill burns. If there are spots without flame then you probably have a clogged burner.