Wow! What a difference new points make. - PeachParts Mercedes-Benz Forum

aircap · #1 02-08-2007, 09:35 PM

If you read my earlier post today, you heard about the death of my old crusty ignition points. I changed them tonight, adjusted them to .014 (my book says .012-.016) and put on a new cap. (Plugs were changed the other day; the new rotor I bought did not fit properly, so I need to swap it out.)

When I turned the key, for the first time since I've owned this car, the engine started immediately. Like instead of: wirr wirr wirr wirr wirr wirr wirr wirr putt wirr wirr putt putt wirr wirr wirr wirr putt pu-putt putt, it was just wirr wi-VROOM. Dead cold, too, with about 20 degrees F ambient temperature. Awesome.

I drove it around a while to get the engine warmed up (the thermostat still needs replacing, as it runs cold), and I can tell it's still not really dialed in properly yet -- still needs a new wireset, new rotor, new condenser (didn't have a short enough screwdriver to get the old condenser off) -- but it's way better.

The old points, by the way, were just gone. The stationary point was literally non-existent...just a hole where it had been. Amazing it had run at all.

By the way, when I was poking around in there, I discovered what appears to be a ground strap of some sort, attached from inside the distributor wall to the breaker plate. But it wasn't attached! I could see that it had been soldered to the plate before, so I fetched a solder gun and put it back in place. What is that thing, exactly? Anybody?

Hope to swap out the wires, condenser and rotor tomorrow. Engine runs stronger now, but still hesitates sporadically when running at speed. Little jerky tugging sensations as I zip along. I'll post again when I finish the ignition side of the tune-up. Oh, and the positive battery cable still needs replacing. I did the negative already...but it's been miserably cold lately and it's kept me from really digging in on the car.

All advice, opinion, conjecture, encouragement and commiseration welcome.

Arthur Dalton · #2 02-08-2007, 09:44 PM

The braided wire is the dist ground strap. It must be on to complete the points circuit to ground and it must be pliable so the plate can advance for ignition timing.
Also, these point systems can be easily/economically converted to Pointless Electronic ignition . A great improvement for short $$$.
Both Crane and Pertronix are decent systems.

meltedpanda · #3 02-09-2007, 08:52 AM

I mentioned in your other post, get a dwell meter, and a good timing light you can really fine tune the ol gal. Then you can get a CO2 analyzer to adjust your carb mix

aircap · #4 02-09-2007, 12:48 PM

Hey, Ron...

Yeah, my pal has a dwell-tach, but he's out of town for the weekend. I hope to hook up with him next week and dial it in better. Also realized after I set the points that I was looking at the wrong spec in the manual...it's supposed to be .016-.020, not .012-.016. So my points are right at about .014 now, a little shy of where they ought to be. Dwell is probably waaaaay high.

I picked up my new wireset this morning, and my replacement rotor (the one I bought had a defect) should be in this afternoon. I'll swap both those out, plus the condensor, over the weekend.

CO2 analyzer, eh? Care to elucidate on that? I know less than nothing about such exotica...but I'm positive my carbs need adjusting. (My mix seems too rich...the exhaust is on the stinky side.) How does a CO2 meter help with the carbs, exactly? Remember: I'm a clueless n00b.

Also guess I should finally invest in a Uni-Syn or the like. I have a twin-carb motorcycle, too, so now's as good a time as any, eh?

Thanks for the comments and advice, everybody!

meltedpanda · #5 02-09-2007, 02:07 PM

From my reseach and from what I have been told, the best way to get the lean/rich mixture correct other than by ear, is with a CO2 exhaust analyzer
CO2 reading for the 220/8 200/8 230 and 250 for model 68-70 at idle (900RPM) is 2.0 to 3.5%
After 71 it goes to 1.0 to 2.5 % There are many other specifics in the test procedure, but I do have all the data if you ever need it.

230/8 · #6 02-09-2007, 05:09 PM

Aircap:

First, no reason for you to get a unisyn for your 220 until you get a pair of carbs to adjust. I am assuming your engine has the original single Stromberg carb. I suppose it could be helpful on your motorcycle duals. A CO analyzer (not CO2) can be a help, especially if you have an FI engine and live with strict smog rules on old cars. If this describes your situation, the GasTester model is really really good and fairly cheap at $200. I love mine, but do not use it on my carbed cars, only for the FI in my SL. You really need to have a good solid understanding of the car and how it works, and how the analyzer works, to realize full benefit from the CO analyzer. For carbs, I like the old spark plug reading, vacuum gauge and tachometer watching skills learned many decades back when that was all we had for diagnostic equipment. They all still work on old cars like ours. Helpful hint...go to a used bookstore and seek out a copy of an early 70s edition of Martin Stockel's "Auto Service and Repair."

For now, I'd recommend continuing on your path of systematically renewing the worn bits and pieces of your basic car. Sidebar...the old points and the fact that they were still working for you should demonstrate their basic value and reliability. The old dears have proved themselves to be tireless and under appreciated ignition work horses for decades. I had a Pertronix on my M180 engine and removed it simply because I have an innate distrust of mystery parts sealed in black plastic and epoxy and that are not repairable with a swiss army knife and a matchbook cover.

I like the old-fashioned method of doing things with my old cars...it is a relaxing bit of therapy from my everyday work. If your 220 is not an everyday driver...even if it is...mastering the old mechanic's skills (the genuine skillls that are based on true knowledge and an understanding of the physical relationships of the machine's systems, not the shade tree mechanic's old wive's tales) all this is extraordinarily satisfying. It can draw you into the Zen of your engine; learning to understand its language of communicating problems, and its operating contentment when all things are right; it will leave you feeling that you have accomplished something tangible and measurable at the end of the day.

Enuf fillosufee...

Good luck with your 220; glad to read that you are making progress.

230/8

meltedpanda · #7 02-09-2007, 06:29 PM

Ok Ok Co:d

250 Coupe · #8 02-10-2007, 02:12 AM

A link to the Gastester and a cool gadget called Colortune.

I have the Gastester and have used it to get a number of cars running better. I used it in this post to tune my 450SEL. I've never used a Colortune but have always wanted one.

Like 230/8 says, you can tune a single carb four with a good ear and patience. I'd bet you can find a carb shop or emission tune up shop that will check your CO for a small fee.

Michael

aircap · #9 02-10-2007, 02:27 AM

Hey, 230/8:

My car has two carburetors.

I'm sympathetic to your philosophy about mechanical things versus electronic things...it's the reason I only buy and drive old cars. (My last few: 1971 Plymouth Valiant, '65 Ford Galaxie, '61 Thunderbird, '66 Dodge Dart, '66 Dodge Coronet wagon, '65 Ford F-100 pickup...)

Thanks for posting. I always value the input of you guys who have had more experience than me, with Benzes specifically and just in general.

t walgamuth · #10 02-10-2007, 06:58 AM

i would put that gap more open. i bet you will be surprised at how much better it runs. it will be weak with the gap too close.

tom w

aircap · #11 02-10-2007, 02:46 PM

Tom: Way ahead of you. I'm gonna mess with it soon. Just have to get up the gumption to go out and freeze my butt off while doing it.

cth350 · #12 02-11-2007, 08:24 AM

ignition 101...

Changing the gap is done to change the dwell. Fiddle with the gap, but get the dwell "right" (as right as you can).

Changing the dwell changes the timing point. Get the timing right at 4,500rpm as per the book.

Get all that right including fixing that ground strap (fix that right now) before touching the carbs.

Dual carbs? Check your motor number, not to mention the car's chassis number. The serial number for the motor is stamped on a flat surface a few inches over the oil filter.

I would leave the carbs for a professional who's worked on them before this time around. Be sure to ask him questions and watch him work. If he won't do it your presence, find somebody else. It's easy, especially if you have a musically trained ear (I don't) and have done it before. But still, there are lots of ways to get it wrong, you don't want to find too many of them your first time out.

-CTH

aircap · #13 02-11-2007, 09:22 AM

cth350: I'm going to check my engine number...people are suggesting it may not be right for the car. Thanks for the tip on location.

Anybody else who would like to comment on this craziness, please do so at my most recent thread. Thanks!

230/8 · #14 02-12-2007, 11:23 AM

aircap:

My mistake on the carbs, I guess yours must be a very early 220 model that is not covered in the 115 CD manual for 1968. It only lists the Stromberg models. I looked in the 110 series manual for the 65-68 cars and there is the twin Solex set-up bigger'n life shown on a 200.

On the Gastester, the link given is reliable from my experience. I bought my unit from this fellow; good service, very prompt, I think he is the importer from the UK.

230/8

barry123400 · #15 02-12-2007, 03:05 PM

Sounds like you are getting nothing but the best advice in general. I just wanted to post that I used to set the timing initially at 3000 rpm. It might be just a little breezier at 4500 rpm. You can check the timing after at 4500. It should be done and good if you did it well at 3000 and everything was in good condition.
I learnt something here I never knew. That is the initial static timing for these engines. The check at 3000 rpm at least is mandatory by the way.
One thought that popped into my mind was the electronic control box. Might the internal capacity of the condensor be different if the car either had or had not the module? I have not really thought this through but you may need the exact required capacity condensor perhaps. I think the old vw condensor might cross refference if you do not have the module. I might check the literature to make sure the mercedes part # is the same with or without the module for the condensor. Only go here if the problem will not resolve. Someone may hopefully clarify this totally as a non issue as well. Just a passing thought.