84 300D, possible short?
 

I'm having the weirdest issue right now with my 84 300d.

I went on vacation for 2 weeks, when I came back I went to start my car, and it started and then immediately died. At first, I thought the battery had died, because I was getting no lights or anything.

After replacing the battery, I had lights, and when I tried to start it, it didn't even crank. All the electronics just turned off. I noticed that if I disconnected both terminals on the battery and then reconnected them, I could get my electrical system working again, but any time I tried to actually start the engine, it would kill all the power again.

Does anyone have any idea what would cause this?

Your car will run with no power whatsoever. Electricity is not required for it to operate other than glow plugs or starter motor.

The fiddling with battery cables strongly suggests that you have a poor battery connection at the main terminals, or a bad main body ground where the negative cable attaches to the body.

Typical with all cars. You have an apparent battery connection issue usually.

When a heavy electrical load is demanded like trying to start. The connection goes open. Best to start by really cleaning the battery posts and battery cable clamps. As for myself I get a little more anal.

I take a twelve volt test light with say the headlights turned on but not illuminating. You have to have a potential electrical load in place for the testing to work.

Touch the center of each battery post with one probe and the battery clamp with the other. You can do this with a voltmeter as well. I just keep going until the test light lights. Or a meter shows battery voltage. This indicates where the electrical circuit is open.

I also treat connections to make them more reliable. Basically keeping them from oxidation. One has to keep in mind that these cars and many of the electrical connections are really old now. Since your battery is new and it is reasonable to assume the posts are clean. Clean the inside of the battery clamps. This is a good starting point.

Your old battery may have still been good. Unless by experience you know it is bad. Always have it tested free at one of those auto parts places that do this. Before buying a replacement. Your description in general does not indicate a short.

X3 on the terminals. I had a "spike style" terminal on my 240D and it worked great, until it just didn't one day. Replace your terminals, preferably the entire terminal + wire itself. Not sure where you are located, but autozone carries 2 AWG cables with terminals already cast onto the ends - worth the price, especially with aging diesels.

every car I have had,I add two extra grounds from battery.Car makers barely make on,and over time they get breaks in the body.I add one from batt, to engine block,and block to chassis

Thanks for the replies everyone. I ended up having someone much more experienced than myself look at it with me, and it turned out that the cable from the battery to the alternator was shorted inside the jacket, which made it so that a visual inspection didn't show the damage that was going on.

Ended up being a fairly easy fix, but I was definitely worried that I was going to be in for a headache.