Fuel Injection and Ignition Timing 420SL

[Mort420]

My first post, so bear with me.

I've just acquired a 1987 420SL (M116.964 engine code). I'm delighted with it and it's running absolutely beautifully. When I brought it home last week I wasn't sure how the fuel injection or ignition timing was set up, so for the sake of safety I filled with Super Unleaded until I could research the point. On looking at the handbook it says "unleaded or super (leaded)", which in 1987 meant 95 octane unleaded or 97 octane 4-star.

There is a gizmo under the bonnet which has 7 settings - "S,2,N,4,5,6,7". It says "EZL ECE" on it and the part number is 015 545 07 28 9251 07 (that's an M-B number, not a Bosch one, I believe). I presume these are ignition timings and that "S" for Super is the most advanced, "N" is for Normal and "don't even think about anything else". At the moment it seems to be set to "N" - it's actually difficult to see where it points but the "N" is between the two "V" marks on one of the clips. I presume "N" is for 95 octane (rather than 91, which I think was available in Germany at the time). If that is correct, then there seem to be two choices in modern conditions - leave it on "N" and use 95, or switch it to "S" and use Optimax or similar. Clearly there's no point in using 98 if the ignition timing isn't advanced for it.

Is that a fair analysis?

The system seems to be Bosch CIS-E. Is that right and is this similar (or identical) to KE-Jetronic.

Regards

Jonathan

 

[television]

Hi Jonathan, you are correct in what you say with that plug and the settings, I must say on mine that I noticed very little difference between the settings when I had mine

 

[Mort420]

Malcolm

Thanks for the reply. Am I correct that the "marker" is the clip marked with the two "V" marks, and whatever is pointing to that is what is set? The switch seems to have one centre pin and only six outer pins - obviously the centre one and one of the outer pins are plugged in on any given setting.

Bosch CIS-E has knock sensors anyway, doesn't it? That should prevent problems with 95 octane. I do remember on my old Audi 5-pot with K-Jet (no electronics) you had to retard the ignition to 10 degrees BTDC (instead of 18) if you wanted to run on 95, and it just wasn't worth it - I soon went back to 98 octane.

Regards

Jonathan

 

[television]

There have been quite a few asking about the ignition settings and the V is the marking point

I did not know that the 420 used CIS, my only dealings have been with the 300 that used KE from 1985-90