'82 300SD Idle Speed - PeachParts Mercedes-Benz Forum

pawoSD · #1 10-12-2004, 11:10 PM

Ok, my 1982 300sd runs great, but it will shut right back off on a freezing (from overnight) startup....we have a 1983 300sd also, and it does not have this problem, it can start up, and run without dying, even cold. Mine starts right up, but if I let off the gas it drops to its real low idle, then shudders and shuts off.....I always have to give it a few rev's to get it going good. I am guessing my idle is real low, my tach doesn't work, thats another issue. I am guessing maybe 600-700rpm tops, the 83 idles at almost 900, and runs very smoothly due to that. Mine runs very very smooth once its warm enough to keep itself running, but otherwise it loses it. Is there a way to adjust the idle speed on mine? I would like to raise it ever so slightly so that it won't shut back off like that.....the idle is so low that sometime (rarely though) letting off the gas after a fast accleration, or a quick stop, will cause it to shut off....its just annoying. So how do I raise the idle speed on a 1982 300SD???

Pete Burton · #2 10-13-2004, 08:24 AM

Idle speed stop is located on the injector pump, between the pump and the block about as far back as the #3 to #4 injector. There is a large, headless slotted screw locked down with a nut. The nut can be loosened with a deep wall socket and the screw turned clockwise to increase RPM

pawoSD · #3 10-14-2004, 01:21 PM

Ok I am definatley going to raise the idle, it shut off on me coasting down a hill when I let off the gas today, not cool. What is the size of that nut at the bottom of the idle screw? I need to go buy a deep socket for that because I don't have any deep sockets. I was also wondering, is it bad to raise the idle rpm? does it put any increased wear on anything if its going 100-150 rpm faster? My tach also does not work so I don't know what speed it will actually be at, I am kinda going by ear and comparing it to our 83, which does have a working tach. I replaced my tach amplifier, and the actual instrument in the cluster, and it is still dead....what else could be wrong with it??? I used a multimeter to check for power, and the cable in the dash for the tach has about 13.3 volts in it, so why is the tach not getting a signal, is it the pickup on the crankshaft? Do those fail? I'd really like to fix it, especially since I replaced both of those items without any success....

tenknots · #4 10-15-2004, 09:51 AM

I also have an '82 300SD. Have you tried the cigarette butt repair? Unscrew the tach amp (black cylinder on the left front fender, an inch or so in diameter if I remember). In the cap is the amp - pull it out, it might take a pit off a pull. Insert a cigarette butt (one found every 3 square inches anywhere on earth) in the cap, put the amp back in, and screw it back. The extra push the butt gives makes the contacts tighter and, voila, the amp works. Done that to two 300SD's and they both still work.

Good luck.

pawoSD · #5 10-15-2004, 07:46 PM

Today I changed the screw on fuel filter (finally) I managed to get the bolt off that was holding it as it was on VERY tight, got diesel everywhere

Filled the new one with a mix of diesel and mystery oil.....its running pretty darn smooth now....as for the tach, I tried stuffing all kinds of stuff under that cap with the old amplifier, and cleaned the contacts and checked the plug, still no go. So I bought a new amplifier, nothing, bought a new instrument cluster pod, nothing....the tach way back used to bounce around sometimes, then it did a little "hop" when starting and shutting off the car, then it went dead, and has never moved since. Am I missing something here, the plug to the gauge has voltage, so there must be something I am missing in getting this working.....

JHZR2 · #6 11-23-2010, 12:15 AM

Did you ever solve the shudders and dies problem you mentioned in this post? Sounds like my car.

pawoSD · #7 11-23-2010, 07:50 AM

Long long ago. It was the spring loaded IP adjustment bolt. It was in as tight as it will go, which caused shaking/stalling/hard starts. I spent about an hour fine tuning it, and it runs beautifully now (I did replace the bolt also). Idle speed remains around 700.

Never thought I'd see a thread I made 6+ years ago appear on the board!