So I was driving my 84 500 SEL one night and it was driving perfectly fine, nothing seemed different (it felt just as powerful as any other day), then I got home and parked it. The next morning, I tried to start it. The engine still cranked strong and roared to life, but only for half a second, and then promptly died. If I try to start it again right after it does this, it will only crank and will not sound as if it is roaring to life again. But if I wait about a minute or two and crank it again, it will roar to life again, but only for that half a second. So what could be the problem here? The things I have checked already that are fine include the distributor cap and rotor, fuel pump relay, spark plugs, and idle control valve. What do you guys think?