GMC Truck

I would like to know what kind of problems a bad ecm (electronic control module)in my 1982 gmc 1500 with a 350 engine over 200,000 km, automatic would cause, sometime it stalls for no reason and wont start again it only fire once when I stop cranking it and when I turn the key off it fires once, if I give the ecm under the dash a beating it will start again be ok for a long time sometime other time it will do this every couple of minutes.I took out the ecm and it seems to be all electronic parts in there. Can one of those part go bad from time to time or is it just that I hapend to mouve other wires around when Ibeat up the ecm with a rench?I dont want to by one for nothing they are expensive ennouf.
Thank you in dvance for any reply to my question.