I know that you have replaced the ballast resistor, however based on your description of the issue with the ignition switch, I would by-pass the ballast resistor by hooking a jumper wire across the ballast resistor. See if the car will start as normal. By-passing the ballast resistor for a short period of time will not harm anything. If the same problem exists after the by-pass then I would suspect the ignition switch. If the ignition switch works OK to crank the engine you can also run a temporary wire from the + side of the battery to the + side of the coil. If the car starts and runs fine then you have identified the problem as the switch. The stalling problem may also be related to fuel delivery as Scooter has suggested. He may have some further thoughts. I am no carburetor expert.

Well, it looks like a carb rebuild will be in my future. I bypassed the ignition switch with the line from Battery + to Coil + and though I got it started, it would stumble, fumble and die.

I'll be reading the existing info on carb rebuilds for a bit.

__________________
63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6

Never owned one with solex carbs. Have owned some of this design engine and still do. Two 114 coupes with zenith carbs.

First spray a little wd 40 around the base of the carbs. Air leaks on these cars are not that uncommon.

Second as the cars sit the gas in the carbs evaporates with time. This leaves a residue that causes issues over the years. I feed laquer thinner into the carbs and let them sit. I either have been very lucky or it is practical.

I have not had to take the zeniths apart and kit them. I do remove the idle jets when the laquer thinner is in the carbs and wait until a good clean flow is established and reinstall them.

These engines also run fine on the laquer thinner. It may be only with the zenith carbs but to me hot restarts are not the easiest. I feel the excess heat even though there are provisions to isolate the carbs still effects them as the exhaust manifold runs red hot.

These setups usually cold start easily in really low temperatures was another observation. I credit this perhaps to Mercedes engineering for the Russian campaign requirements of the second world war.

Anyways these thoughts are just made by an amateur. Incidentally one possible reason for the first spark plugs appearance and suspected miss. You will find a plug on the intake manifold towards the front. If there is any air leakage there verified by application of wd40. It is leaking. Also try to check for air leakage on the manifold flange up in that area as well. It can easily upset the air to fuel ratio the cylinder needs. That first plug did look or sound lean to me.

What I do not like either is the heat dampers being non operational under the carbs. A not untypical issue. I am just an old car hobby guy with some experience over the years.

I might take a temporary break from the ignition at this point and get into the fuel system area. Although once again I never dealt with solex carbs for some strange reason. That does not lessen the practicality of some of my thoughts at the same time.

Great little engines when working well but not the best on fuel consumption. I seldom post in vintage cars. There are just too many guys in here usually with superior knowledge. Plus a lot more experience.

I had but one fixed rule with these engines. The valve adjusters in all the earlier engines did not have enough of an interference fit. Never neglect to check the valve clearances at the recommended intervals. It will cost you a burnt exhaust valve if those valve adjusters moved too easily. In fact there is a torque spec to replace them at somewhere.

On some of the increased interference ones I needed the rocker arm out of the way to get a socket on them. This did away with the fifteen minute check and adjust were needed but I actually preffered them.

After a time I will drop back onto this portion of the site and see how you have done.

Barry,

I tried to run some of the tests you suggested but I couldn't keep the car running long enough to be conclusive. I got it started and sprayed some WD40 around the plug on the intake manifold by #1 cylinder. This is the vacuum line to brake booster.
It may have been my imagination or coincidence but it seemed like the idle increased in ferocity when I sprayed in that location. I was keeping a fast idle (maybe 2000rpm or more) to keep it from stalling. After that seeming burst, I couldn't tell if it was sucking WD40 or the windage from the cooling fan was just blowing back and disturbing the spray around the plug.

The carb area is fairly leaky. There's always been signs of gas in that area but it's been that way for a long time.
If you are suspecting vacuum issues, wouldn't it run generally crappy all the time? What it does is run well when it is going but then it stumbles until the stumbling is sufficient to kill it.

Interestingly enough MB still has parts available for the manifold flaps. If the carbs come off which they likely will, I'll be endeavoring to get those working again.

__________________
63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6

Sorry it took so long for me to check back. Remove the fan belt. The engine can run for a short time with no water pump and you want to localize the leaking areas.

I am not going out in the garage to look at the layout. As long as wd40 was not getting into the air intake of the air filter you do have some issues. It takes very little air intake leakage to upset the applecart. You do have the two o rings between the filter box and the carbs? I assume a similar set up to the zeniths.

Incidentally you check timing around 3K revolutions on these engines I remember. Although others have perhaps been okay with checking them at idle. Common sense to me is to check them at both speeds eventually. This is probably still in your future though.

You have to find and eliminate the air leaks into the manifold system if they exist. Otherwise the suction forces are lower for the carbs. Or as I suspected in your case the gas to air ratio is too low on that front cylinder. Or even a combination of both is possible I suppose. The air leaks are suction in nature. In general I would not expect to see gas where they were. There of course like all things can be exceptions.

Try to remember that it has been some time since I worked on these engines. Plus it was not as a working mechanic. When they are right they are nice runners. I will check back more frequently on your thread. Between gummed up carbs and air leaks corrected you might be okay.

When the engine goes to idle basically only the idle circuit is providing the fuel. Those passages do like to gum up I have found. On the other hand anytime I thought I might be right the wife has managed to correct my line of thought.

Barry,

Thanks for the reply and no worry on the timeliness of checking in. I'm making very slow progress on this as I have too much on the plate now.

The connection between the filter box and the carbs is just a metal clamp fitting, tightened with a screw. There aren't any gaskets; mine has the Solex carbs.
I would check timing at varying RPM's if I could, I assume this is to check advance.

I'm looking in the EPC to see what's involved with the brake booster vacuum line. If there is a leak there which is likely, I hope a new fitting and seal ring would fix it up.

Sometimes I get frustrated at all the little things wrong with the fin and feel like I should tear the whole thing down and rebuild it all. It's a good runner overall but she's almost qualified for an AARP card. A little refresh seems justified.

I appreciate your help. BTW, what do you have stashed in your garage?

__________________
63 220S W111
76 300D W115
2013 VW JSW TDI M6

previously-
73 280 SEL 4.5
86 300E 5 speed
2010 VW Jetta TDI M6