1983 280sl M110 motor....Was running great but the cap and rotor were worn and the wires were of unknown age. Sooo......out with the old and in with the new. New Bosch cap, rotor and plugs and a set of Beru wires. Took old stuff off put new stuff on. Checked gaps, torques, wire routing , part numbers etc etc. Now the car runs like s**t. Black smoke spews out of the tail pipe. It might be worth noting that the sparg plugs coming out were deposit free and a little white
(lean? advanced timing?) and the new ones are noe black and sooty (rich? retarded timing?) Any ideas?

Assuming you got everything back together correctly, used the right plugs (w7d copper), and didn't mess with the mixture, or knock any vacuum lines off, it is probably coincidental:

- Cold start valve continuously spraying or leaking (try disconnecting)

- Diaphragm in pressure damper has hole (disconnect vacuum line)

- Warm-up compensator gone nuts (try unplugging)

- O-ring in fuel distributor suddenly disintegrated

Triple check the wires are in the right firing order. Also check that the Cap is properly seated and indexed on the distributor. If everything checks and you still have the problem ... put the old Cap back and see if the problem goes away. I have had the situation where the Cap was wrong (even when it fit and had the right part number) ... and have had new Caps that were defective.

Beyond that, I would not assume something else just happened to go defective. Focus on the question "what changed" and investigate the obvious and work backwards from there before asuming something totally unrelated decided go bust given the probability of this happening is remote ... unless you did something like remove your plugs with a hammer

Disconnected vacuum lines would be the next area to investigate beyond this being a spark related issue.

Would you believe it's probably the ignition wires? The coil wire is likely carbon core and choking the spark down to nothing.

You wouldn't believe how many times parts places sell you the wrong stuff and don't know what's right for your car. I have the right set in stock if it turns out to be wires. You can use W9DC plugs. Sounds like it was OK before you fixed it ~)

Thanks guys....I have put all the old gear back on (except plugs) and no change in the poor running condition. I will put the old plugs back in but I really don't think that will solve anything.I will try all the troubleshooting suggested this weekend.

You must have dislodged something! A possible culprit would be the pipe connecting the MAP sensor (manifold air pressure). If there is a leak in this pipe the mixture becomes super rich.
I had the sensor actually fail and my fuel consumption pretty much doubled. You could easily have accidentally disconnected it.
Unfortunately, I have no idea where the sensor is or the piping on a 280 (mine's a V8).

He may have dislodged something but it's not the MAP sensor - this is K-Jet, not D-Jet.

I that case it could be the warm up regulator. The engine will run very rich when it quits working. You may have knocked a vacuum line off or something like that but they can fail at any time.

Thanks all. I will try the various suggestions tomorrow and keep you posted.

Well, I removed the new bosch w7dc plugs and re-installed the old autolight 64 plugs. Much improvement however not there 100%. I pulled the wire off the cold start valve....no change. I pulled the wire off the warm up compensater...no change, however,one of the electrical tabs on the compensater had corroded and was still in the plug end of the harness. Guess I will be changing that. Funny thing about the compensater, every picture I have seen of one shows, it seems, a vacume line.....mine has none.
As far as plugs go...where should I go next? Is there a big difference between the w7dc and the w9dc? Maybe I should stick with the autolites....