Hi all. Haven't posted in awhile. My 82 300D Turbo is not starting so I have done some testing and have narrowed it down to the starter solenoid I think. Here is what it is doing. I put the key in turn it to the glow plug setting light comes on then goes off I turn it to start and nothing. The started doesn't turn over. But the lights dim. So test the starter by shorting out the two large terminals on the solenoid and it turns fine. here is where I am confused to test if the solenoid is ok or not I tried putting a test light from the positive terminal on the battery to the small screw on the soleniod and the light came on. The thing is I didnt have the key in yet. I thought it was supposed to only come on when you turned the key to start. Thank in advance for any help.

You did your test wrong. The test light should be from the starter terminal to negative. Putting it to positive is passing current through the test light as if you were trying to engage the starter.

Are you hearing the solenoid on the starter clunking when you're turning the key? If not, try starting in Neutral. If the engine cranks, your neutral safety switch is failing or the shifter bushings are worn or missing.

If the solenoid on the starter is clunking when you turn the key, the solenoid is likely worn out and in need of replacement.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

That makes more sense I was wondering about that.so I will try it again tomorrow only hooking it to the negetive. I tested the neutral switch and it didn't seem to be the issue. The solenoid did seem to be clicking when I turned the key. Just not turning the started over. Thank you