LD Max. Run that by me again, please. From which authority comes this advice of turn left or right depending on which side of the engine cowl the fire is seen?
I must admit that I have never heard of that little gem. So if the forced landing field you have spotted is on the left of the aircraft and the smoke is coming from the left side of the engine, then it would seem against normal rules of airmanship to deliberately carry out a turn away from the field simply because of smoke/fire etc.
Is your information from the aircraft type manufacturer's POH and if so, which specific type of aircraft are you referring to?
If you mean that the aircraft should be sidelipped in order to direct smoke/flames away from the aircraft as much as possible - then that is another story altogether. As long as you remember that some high wing types can bunt over violently if more than a certain amount of flap is extended during a strong sideslip manoeuvre.
The C150/172 series comes to mind where flap extension can shield the tailplane area in a sideslip resulting in tailplane and elevator loss of effectiveness.
Anyone that has time on Cessna 150/152 aircraft will be aware that very often the fuel valve will be either stiff to turn off or more usually completely jammed on. This is because pilots rarely exercise the fuel valve by closing it after close down from a normal flight.
A stiff fuel valve should reported in the technical sheet for rectification before next flight. If the fuel valve is immovable then the aircraft is deemed unairworthy.
A engine fire in the air is deadly if you cannot turn off the fuel valve. Don't ever leave it for the next poor blighter to find out.