1984 500 sel stalling.
 

I have a 1984 500 sel, 260000 miles, runs fine except that the engine stalls, (or shuts of ) by itself from time to time. It will often restart by itself within about 4 seconds if the car is moving.
If it shuts off while I am stopped at a traffic light I must shut of the ignition and then it easily restarts. My mechanic changed the fuel pump on it and said that would take care of the problem, but it didn't. What else could be causing this problem?

I have/had the same problem. I have a 1988 300SEL... and it did that after atleast an hour of driving. I haven't had this happen to me again in the past month and a half, but I am still going to have my tech check it out. From what I heard, it could be something with the pressure not being at a level where it takes in fuel. I am curious as to what others got to say about this.

Well I got the problem fixed. I took it to Wurster's Foreign Car Repair in Franklin, TN. As soon as I told the owner what the car was doing, he said he knew exactly what the problem was.
He replaced the "fuel relay" and the car has run fine since.
Hope this helps others with the same problem.

Wow.. must be the first occurence on the ShopForum of someone taking it to a tech and *actually* getting the car fixed :rolleyes: .. well I suppose you did have 1 b******* diagnosis to go through first.

Sometimes I wonder about some of the techs you get in the USA, do they actually diagnose the problem, or just keeping making you buy stuff until eventually they hit the right part and the problem goes away?


later

stalling
 

Help ! I have the same problem with mine. did they happen to show or tell you where thet relay is located ?

Thank

Scott Lumry

On a 190e and a 300e, and probably your car, It's a little black box about the size of a cigarette packet, with around 7 pins on the bottom on the right side, and 3 or 4 on the left side.

In these cars, it's found behind the battery, next to large metal boxes that are engine ECU and abs ECU. There's a chance on your W126 car, it's inside the cabin behind a panel in the front footwell's - anyone confirm?

Next time the car won't start, see if the fuel pump runs for a second or so when you switch the ignition on - it should buzz. If not, the relay most likely isn't switching on so replace it. (I actually repaired my, a bad solder joint).


later

Nope you missed this one. The fuel pump relay is located right of the brake booster on 126 bodied cars. It is identified by it's markings on top of it. It will have the word xZYL (x=number of cylinders the car has) along with an RPM limit which varies depending on which engine it has. Also your test is not a valid test since there are 2 sets of relay contacts inside the relay box. One for when the key is on and the car is running and one for when the car is cranking. The reason for this is the crank sensor does not make enough voltage to close the relay during cranking so the relay gets a signal from the starter circuit to turn the relays second contacts on.

Now sir I have a beef with your comments here! I didn't see you offering this gentleman any help before he had his problem fixed only snide remarks about us Americans being hang an hope mechanics. What are your professional credentials? After talking with my professional mechanic friends from the UK I know one thing and that is there are plenty of hacks/gomers world wide. So as my mother would say, if you can't say something nice about someone keep your mouth shut!

fasthair