Try pressing E then 1,2,3,4. E is the engine select and 1,2,3,4 is the engine number you are selecting. If you hit E then 1,2,3,4 all at once it should reselect all the enges. Only needs to be done 1 and 2 if there are only 2 engines on the plane. Hope that makes sense.
Two rules in aviation, don't hit anything and don't run out of gas, cause if you run out of gas yer gonna hit something.