Did I find the magic button?
 

560sl. poor idle, numerous what if posts. Lately had trouble with the starter, and the car bogging down on acceleration. Changed out the fuel filter and went for a ride. No better on accel, maybe even a little worse. Now the starter is even worse so I'm thinking at least check the battery first.

I opened the flip out in the trunk and the battery looked brand new-but....hey, what this plunger looking thing mounted next to the gas inlet? The handle is clearly out-so what have I got to lose.

I pushed it in, cranked it and voila-like new, no bad crank, immediate startup, took it for a spin and it drove like a new car-ok, cept' for the brakes and the mediocre idle.

Cheapest fix I ever did. What is it, and what did I do? (I assume it's some sort of fuel safety valve that I should have opened before I messed with the filter (I did open the cap..)

Thanks. I'm gonna sleep well tonight.

j. Boggs

Was it the manual unlock for the fuel door?

I dunno?
 

It has 2 or 3 vacuum connections to it so I assume it was some sort of fuel shut off but I suppose it could have been the door open. Maybe it is some sort of aftermarket alarm feature...heck I'm not sure.

Anybody have reference to a lunger thing in their CD or manual?

It looks like one of those things you push on a tv game show if you think you have the answer-except its mounted sideways.

All I know, is my car now is running pretty much normal, no starter problems, no bogging, but the idle still stinks.

J. Boggs

sounds like it is some sort of Reset button. Something simular in concept to recet buttons on the newer electrical sockets.

I am thinking that maybe it was the fuel door lock mechanism that is vacuum driven. You might have had a leak going on there, affecting performance.
If this is not the case, I will need to see if I have one of those magic buttons on my cars...:D

To all that have read this thread: take evasive action immediately!
I'd start looking over my shoulder very carefully if I were you. You've just stumbled into one of the key revenue sources MB built into the 560, and an example of MB engineering on a level you never suspected. It's the immediate-fix button, which is otherwise known only to dealer-employed mechanics and is responsible for the incredible profit margin in servicing these cars, since using it fixes anything that's wrong and still allows the dealer to bill hours of labor. If MB finds out that you know about this....or that any of us have read your post.... :D

Correction to my prior post. It's the vacuum element/actuator for the fuel door lock. It's not operated by, or connected to any part of the engine vacuum system. If it leaks it won't affect engine performance. The "button" in question simply allows you to unlock the fuel door in case of a central locking failure.

i really like the golden rivet theory.

say.....i sure hope that alleged alliance with MB, MS & AMD to track all readers of this forum is just a rumor.

And cbdo since you spilled the beans i nominate you to take the "hit" from MBHQ

Remember, Don't turn around!

Now you guys did it!! You figured us out. After contacting HQ
it has been decided that you all have to go! MBUSA will be sending you all complimentary vouchers for a free tour of the nearest MB facility. Once there you will be given a timely demise.... I mean timely demonstration on car care.
Otherwise we will have to dispatch our Gestapo Roadside drivers
to come stop by and loan you their tire iron.
Resistance is futile, your cars are loaded with all kinds of
secret tracking equipment. (For saftey of course.)
See you soon.
DR.D