92 dodge van 3500

hi my brother was playing with our van and now it doesnt crank

i checked the battery it has a full good charge
i checked the coil and plug wires they are good
the check engine flashes once when i turn the key so i know the computer is good

what should i do?
is there anythingthing else?

what do you mean "playing" with your van? what was he doing to it?
how did you check the battery? have you tried starting it by jumping it from another vehicle or battery?