I've noticed a very interesting feature of the accelerator pedal. With the car in drive and at idle, if you apply slight pressure to the pedal it will give about a half centimeter and come to stop position, which can definetly be felt by increased resistance. With the pedal in this position there is no increase in RPM, however, there is definetly more torque going to the wheels, because the car will ever so slightly lunge forward even on a slight incline. The mechanics of this operate so smoothly that I'm sure it must have been designed like that for some reason? Has anyone experienced this little marvel?

Bill is right...that's how they work.

You can keep your foot on the brake, and shift down to 1st manually and feel the same torque effect--it may even make the car start to creep forward, if you don't have the brake pedal pressed hard.

Mike

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1979 300 SD
350,000 miles
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1982 300D-gone---sold to a buddy
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1985 300TD
270,000 miles
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1994 E320
not my favorite, but the wife wanted it

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I read your post and decided to observe the pedal behavior. It appears there is play in the accelerator pedal. There seem to be no increase in RPMs until a resistance is felt. However, under the hood, the bowden cable is being pulled and the injection pump remains at idle position until all the "play" is taken up. When the resistance in the acclerator pedal is overcome then the car accelerates.

To me, the way the pedal is set up in the 300SD is hard to understand. There so many linkages that it become unclear what does what. If you understand the system, I'm sure you can customize the shift points.

If anyone CAN explain how all that linkage is supposed to be adjusted.Do you start at the pump or the pedal?The isolator? on the horizontal linkage?The vacuum modulator on the cam cover?I've done a search before but never found an answer,please help

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Greetings Kyle,

Start your adjustment at the pedal. First look at the nylon throttle rod bushing at the firewall to ensure it is installed in the firewall. If it's not, there a a lot of play right there. Two screws holds this bushing to the firewall, and have to be removed in order to reinsert the bushing into the firewall. Positive pressure on this item will not force it into the wall, and you'll see this after pulling the two screws out, it's a two piece bushing. If this linkage is fine then follow on down the line and adjust each end socket until the play or slack is basically non-existent on each rod to socket connection. Don't forget to lube each socket end as you go. Some prefer tranny fluid, and others use lithium grease, your choice. After each connection has had it's play removed to taunt and not extended, test drive your benz for performance, reaction and shift points. If shifting points seem off, do a search on this site as adjustment of this has been covered many times over.

Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

In all of my diesels, I adjust all the linkage so I get maximum potential out of the engine and there is absolutely no play at all. If a fly lands on the acclerator pedal the rpm's will increase

Thats just the way I like my cars.

Thanks Charles,what happened with my car was the 'stop lever' with the rubber isolator seperated on my way home from the Vancouver Indy.The AAA came out and rather than tow me home he used a hose clamp to tie it back together.That worked until I got a replacement from the dealer,but when I put it back together I did as you suggested starting at the pedal and removing slack.When I got to the linkage at the cam cover the fork(on the stop lever)and the mating part didn't touch.I thought that they should and adjusted everything to make them engage.Now there is no slack at the pedal and the car seems to go better but I don't think it's right.The transmission doesn't behave the way it's described above.I have found a link to the transmission adjustment,but I have never found a thread that gives specific,detailed instructions.Does anyone have a M-B 123 manual that they could look this up?My chassis number is 199986.OK that's scary,I've memorized it Thanks in advance.

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

Greetings Kyle,


Does your linkage cross your valve cover and one rod runs along the passenger side down to the tranny? If this is the case, then adjustment of your shift points are quite simple. Disengage the ball socket at the point where it runs along your block at the valve cover. Pull this rod up extremely taunt, may have to push up from the tranny end to get rid of the slack. Adjust the end socket so it just snaps to your ball that crosses the valve cover. Next, insure that the valve cover cross linkage is taunt and that the slop is taken out of it. If everything from the pedal to this point has already been adjusted, then you are done. Your car will shift and downshift properly and very precisely. This means that your car will maintain probably a slightly higher rpm before shifting to the next gear, as it should, especially on full throttle starts. It will also respond to downshifts on upgrades very quickly and keep you from lugging or having to resort to the downshift button. If you shift is controlled by cable, the exact same procedure takes place, but you will need to adjust your bowden cable for the same performance.

Hope this will help you get your Benz back to performing like it was designed. I am assuming it is a non-turbo diesel, as your model year is an '80 Trust me, don't expect a rocket when you are done with it. My '80 300TD non-turbo isn't either, but I live with the great fuel mileage, and drive the '84 300SD turbo when I need the feeling of turbo power. It does make all the difference on acceleration.

Charles

__________________
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan

Hi Charles,no mine doesn't have the rod on the passenger side,my transmission is strictly vacuum controlled by the modulator(?)on the cam cover,I think.My linkage consists of a vertical rod from the pedal to the horizontal rod you mentioned before,there's an adjustment between them.The horizontal rod is secured in the firewall bracket (it seems ok),goes forward to the stop lever, where the two slide into each other.The stop lever didn't come with the nylon bushing and when we looked for it on the dealer's computer we couldn't find a part #.We assumed it came with the stop lever,there is a lot of play at that end.Moving along with the linkage,the horizontal rod has a vertical bracket with a ball,the socket rod goes horizontally toward the passenger side to a horizontal cam lever that is pinned to a bracket on the cam cover.There is another horizontal rod that has a slip joint,it connects with a socket to the ball at the top of the stop lever.The slip joint provides that shift from 2-1 mentioned above,I assume The horizontal cam lever actuates a vacuum control that I did find the adjustment info for (the transmission).From the stop lever there is another vertical rod to the injector pump.The relationship between the stop lever and the horizontal rod back to the firewall is confusing me,there is the fork and catch at the bottom and a slip joint at the top,if you adjust one it throws off the other, .I'm sure there is some Vulcan logic in there somewhere I just haven't found it.

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