Whats your diagnosis?
 

Well, we are at a loss here with our 1985 380SL. We have gone through 3 fuel distributors and finally got one that seems to work. But.... we have one cylinder that just won't clean up. The plug is really dirty. And the car smokes after sitting at a light, like its loading up. Does any one have any idea what to look at next? Should we pull the top of the motor apart and look into the cylinder? Any suggestions would really be appreciated. :(

Injector? Cap/rotor? Plug wire? O2 sensor? Fuel pressure regulator? What was the reason you replaced the fuel distributor to begin with. More info!

The car had sat in Phoenix for 8 months and the distributor had gummed up, so we replaced it. We also replaced the injectors, cap and rotor, O2 sensor, & plugs and wires. We were going to try to replace the one injector and see if that helps. When we first got the car, it smoked all the time. Now, it only smokes when we take off from a stop. We also had to work on the vacuum lines, they were set up incorrectly. We were told when we bought the car that it needed a valve job, but we're not real sure if thats right or not. Could the fuel pressure regulator mess up just one cylinder?
Thanks for your time! :)

it might not need a valve job, but I bet the odds that it needs new valve seals are pretty good. (might explain the dirty plug too) How is your oil consumption?

No massive consumption by any means, but we can smell fuel in the oil. And that cylinder (number 8) throws 160 pounds when we crank it.

Any more ideas?

thanks for your help!!!!

Is the dirty plug wet or dry?

Dry means that it is running rich or not firing all the time. Since the rest of the engine is not rich, chances are it's an ignition problem.

Wet means that it's burning oil, so probably a valve stem wear problem or tired oil seal.

I'm tempted to suggest valve seals.. do your plugs look like this picture? That's how mine get. Sometimes they have lots of grey crumbley crud on, a bit like ash.. that is caused by oil too.

This plug is coming out fuel saturated. None of those plugs resemble what our plug is doing. We originally purchased a "used" fuel distributor and we're not sure if that threw some dirt into the new injectors. The funny thing is, when we gap the plug really wide, it starts to clean up a bit and runs better.

Thanks for taking the time to help!

An easy test of plug, wires , inj., etc . is to swap them from the bad cyl. with the ones from a known good one and see if the problem moves with the swap...
Specially plug wires....

Hi there,

I am not a mercedes technician, but would bet, that you have one injector "dripping". i.e. not closing all the way.
If your fuel distributor was gummed up from sitting, a gummed up injector would not surprise me.
The reason why the engine runs better with a larger than normal gap is, you are getting a bigger ( stronger ) spark. Hope this helps you a little.
P.S. If it was my car, I would try a triple dose of fuel injector cleaner first.