1976 Mercedes Benz 300d help

The reason it will not shut off with the key is first of all, it sounds like you've got either a bad vacuum pump or you recently had its service, and when they changed the oil filter. They knocked loose or damaged a vacuum line, check all your lines, make sure they are connected, if they are. You have a bad vacuum the kit for the vacuum only cost about $12 and the overhaul is easy.

Okay listen up, the vacuum pump is located on the left side of the engine in the front, it is round, made out of aluminum, it is bolted on, with six Allen head bolts, after you remove the there are seven screws that you have to remove on the front where the diaphragm is located, I'm assuming you have a kit to overhaul it? Once you remove the screws and you see the diaphragm. Be very careful, because it has 2 one-way valves, that have to go back in the same order, or the vacuum will not work. Good luck.

The reason the battery is going dead is either the battery is no good. Or you have a short, if you have not fixed it yet, me know