I have recently bought a 1975 California model (manufactured 9/74) Mercedes 280. It has a Solex 4a1 carburetor, air injection and points-and-condenser ignition system with an electronic module. The car also has a 4speed automatic transmission.

Current problems:

1. Needs intermediate driveshaft bearing. I am sure this has nothing to do with idle problems.

2. Shifter probably needs adjustment. The car does not always get into park from the first try (likes to roll around with the shifter in Park position) It does get into Park "for real", sometimes it takes more that pone shift to reverse and back into park. The car also sometimes refuses to start in park but starts in neutral, when the trans is in neutral the shifter does not line up with N mark. Could also be a bad switch on the trans. I suspect that this may affect the idle when the car is in gear.

3. The car does not hold idle when the engine is warm and the transmission is in Drive (tends to shut off at stop signs and red lights). I chased out a few vacuum leaks and it does seem to idle OK when cold, or when in Park.

4. The ignition seems to miss sometimes, mostly on warm-up, especially in wet weather. The distributor cap is new and looks good. The wires look ok. It needs a new rotor for sure. The distributor seems to be completely lacking the vacuum advance unit. Either it was removed, or the distributor is some kind of an aftermarket unit. It is also turned all the way, so things are definitely not right.

I plan to fix ignition fist, then deal with carb.

Q1: Will an electronic distributor from a later M123 M110 engine be a direct bolt-on?

Q2: If so, which years/models should I look for?

Q3: What is the difference between distributors for fuel injection cars and cars with carburetors?
Note: I am planning on gutting the points-and condenser system and going with electronic (VR-sensor) distributor and MSD 6A or megasquirt 2 for ignition. I am more leaning towards the latter, because I would like to eventually go to fuel injection, once I get my grubby hands on D-Jetronic intake manifold.

Q4: Is the lack of vacuum advance on the distributor a definite "modification" or is it some weird California emissions related variant.

Q5: Which SMOG vacuum circuits should I get rid of first? For now I want to vent the carb float chamber into the air box, exorcise all air injection then EGR. In that order. Feedback is welcome.

If you are still in California then you cant remove ANY of the smog stuff. If it had it, it keeps it.

A M110 is a M110 whether it is in a W107, W114 or a W123 so the distributors are the same. The control unit is the sticky bit. Go to a Pertronix or Crane set-up before you attempt the transistorized electronic set-up.

There is no vacuum advance. There is a vacuum retard. Advance is done by mechanical centrifugal means with springs and weights.

It's 1975 model year, manufactured in 1974, so it is not subject to smog check. Consequently one can remove all the smog equipment without getting caught. I feel pretty good about this idea, because the car has no cat by design anyway, so chances are it will run cleaner with a good ignition system and fuel injection than it ever did with 40 year old carburetor. I prefer to follow the spirt of the law, not just the letter of the law. The end goal is better emissions and I have every intent on getting there.

I was under the impression that W123 and W126 (et least the Euro W116/280SE, W126/280 and W123/280E) had a different ignition distributor with VR-sensor (Variable Reluctor) as opposed to points and condenser on the W114. I wanted to upgrade to VR sensor because:
1. I can probably get a used or rebuilt stock distributor relatively inexpensively, somewhere in the $100 range as opposed to $400+ for an aftermarket distributor. I'll take a closer look at the distributor in my car, but lack of the vacuum retard is not a good sign. Chances are, I am going to need a distributor anyway - might as well get a good one. If the problem persists, the plan was to exorcise OEM ignition control altogether and put MSD 6a or another aftermarket unit. The used MSDs are abundantly available under $150.
2. I believe that VR sensor is superior technologically to points+condenser anyway. In my experience it was much more reliable.
3. Rather than spending $100-$200 on MSD I can spend an extra $100 and get Megasquirt 2, use it to control ignition for now. This leaves upgrade path to either TBI or a custom system based on D-Jet manifold wide open. Both MSD and Megasquirt work better with VR than points+condenser in my experience (YMMV).

Nothing wrong with the VR set-up but before I'd go through the trouble of wiring in the control unit I'd switch to Crane (optical pick-up in place of the points) or the Pertronix system which also eliminates the breaker points.

If you are going MS anyway then why not go with a toothed wheel and pick-up. Use MS to control the spark and remove the dizzy from the equation. You'd have to go with EDIS of some sort.

I'm going with the Ford wasted spark set-up I wrangled off a Taurus in the pic-n-pull.

At the moment I'm using the Crane optical in my coupes ('72 and '74). You can have the Crane set-up from my 280 (being sent to great parts warehouse in the sky, alas) for the cost of shipping. PM me.

MS doesn't really like the Crane set-up (look under my postings of M115 TBI to see my experience) so that is something to take under consideration.

Do you know of a good source for trigger wheels? I'll gladly buy one in the near future, when I go to Megasquirt. For the immediate future I am trying to get the Mercedes to run reasonably well without spending a lot.

Sent you PM, thanks a lot!

I'll use the Crane setup for now, it's gotta be better than stock points and condenser anyway.

Correction: the PMs are working, just not making it to the sent folder for some reason.