Hi,

I had the same problem with my 1991 w126 420SE. After driving for several hours in a rainstorm and parking it for a week in the garage, it had a hard time starting, but finally started OK. I then drove it for a couple weeks, and the problem got progressively worse (stepping on the gas, it "hesitated", and eventually would almost die before finally deciding to go).

Then it completely refused to start. I live in Munich and have "ADAC" insurance, and asked them to take a look. The mechanic came to my garage at home and determined that the "Kraftstoffpumpenrelais" ("KPR", located under the hood next to the windshield), which controls the fuel pump, was defective. When replaced, I could hear the fuel pump starting again when turning the ignition key (before activating the starter.)


It then started OK, but still hesitated when stepping on the gas. This got progressively worse for the next couple weeks until it finally would die if I stepped on the gas too quickly.

I then had the spark plugs and cables replaced, which I had wanted to do for a while anyways, which seemed to help a little, but it was still not as I was used to.

Finally in frustration I took it the the big, central Mercedes dealership here after my regular Shop recommended them ( I know, it sounds strange.)

They replaced the "Zündspule" (the ignition coil which is connected to the distributor cap by a single cable), and things are pretty much fine. It still hesitates a little, and I'm thinking about having the computer checked.

The next step would be the distributor cap and distributor.

P.