300TDT won't start!

[dieseldaddy]

Please advise:
My 1981 300TDT has been doing this on a somewhat regular basis since February.
Drive the car for a while and park it in the driveway. Attempt to start it 20 minutes later and NOTHING! Just a single click when key is turned past 'glow'.
Sometimes even the glow light and fasten seatbelt light do not come on, but all the ones to the left do...
Battery is sometimes discharged, (have had 2-Optima red top batteries since February) but a quick charge or a full overnite charge and the car starts right up! Hard to believe it is my starter, but that is a possibility I guess.
Here are some things that make me think that it is NOT my starter:
1. Symptom of clock losing 15 minutes seemingly overnite a day or two before this happens.
2. Battery discharging when not running. This is even after long drives (i.e. 25 miles+)
3. Turn signals are *FAST* at idle but slow down to normal when accelerating or steady speeds.
** drove for 35 miles tonight after a full charge of the battery and reconnecting the original wire and STILL turn signals were wierd when I got home...
HISTORY:
There was an aftermarket alarm system that was removed prior to me purchasing it. There was an original purple and white wire near the ignition under the dash that was spliced to jumper the alarm. (I removed that today, and re-dpliced the purple and white back together.) This 'jumper' was loose and most of the other times this happened, I could jiggle the wire and presto, car started right up.

Battery charged and engine off reads 12.5 Volts.
Battery at idle reads 13.9 Volts. This tells me that voltage regulator and alternator are fine...right?

Headlights do not flicker or dim when A/C comes on, etc. I really do not know what could be wrong here.
Below is a picture of a connector right in front of the battery tray that was disconnected up until a month ago. That was the last time (before yesterday) that i had this problem. I though I had it fixed!


What are these wires going to? I could not trace them. I have more info and history, but this post is getting way too long...

Thanks in advance, as this is my wife's car and she needs it to haul our two small children this week! (and I ain't giving up my 240D!! )

[Ron Johnstone]

I'd bet on a flaky ground. Carry a jumper cable with you and when/if it happens again, try connecting the negative battery terminal to a good ground connection on the engine or the frame, then try to start it.

You might closely examine the battery connectors where they join the actual wires as you can get corrosion at that point and it is essentially invisible to a casual inspection. I'd also recommend looking at the existing ground terminal connection at the engine.

[dieseldaddy]

Thanks Ron!
I will check the connections tonight.
Where is the actual ground at the engine?

[Ron Johnstone]

Just follow the - wire from the battery. Easier to look than to explain it.

[dieseldaddy]

...duh...
Thanks, and sorry.
I will follow the lead and post what I find. I will clean all connections, even if they look clean.

Thanks again.