I never knew I wanted an old car until I saw one for sale one day driving to daycare. I knew it had to be mine. It is a 1970 250C. The car is in fabulous condition. Original paint but you can tell that some light body work has been done....car looks great the way it sits but a new paint job and it would be unreal. No rust that I can see. The interior leather looks almost new. Same with everything else inside. The engine was rebuilt 10,000 miles ago. Total miles it has 108,000. The air con does not work (I was not too concerned). When I test drove it the car would stall if you were not real careful when you came to a stop when you hit the accelerator. I paid the guy $4,000 for it, he wanted $4900 (I now am finding it may of been too much). Within 2 days of buying it the car went from stalling if you hit the accelerator to much at a stop to almost always dying at any stop unless you can keep the RMP's up. I am also having a tougher issue getting it going and warmed up. When you are driving its great....I have spoken with some people and they say I need to have the carbs rebuilt. The carb shop in town said they would do it for $680 but thats not taking it off and even putting it back on. Also the heat risers are stuck...does anyone know how involved that is for $$ to fix? I am not a mechanic nor did I ever envision being one. I love this car...do people drive these that are not mechanics like most of you online here? Should I just cut my losses now and not fix it ($1,000 I am guessing just for the carb issue...less alone how much for these heat risers) and see if I cant get close to my money back out of it? Am I in for a life of dissapointment of things constantly breaking? I want to drive around in this and love it but dont have unlimited funds and I am not a mechanic. Ohh and another thing...its leaking oil from somewhere..small spots on floor. I have not been underneath it to find out where yet. The previous owner always put 90 octane...I put some 92 in with the tank half full and that is when the problems became worse either by chance or? Would putting some fuel carb cleaning additive into the tank help? Any help or advice is great appreciated....does anyone know of someone in MN that works out of their home on these?

Lost in MN

When I was looking at the choke flaps...if I almost close the back one after starting the idle starts to run great. If that helps at all. Thanks, JR

It would seem often enough on these old cars that the problems can be fixed very economically. The advisors probably tell you the knee jerk answer to rebuild the carbs because they know that's the best way to solve all carb problems. Given the age of the gaskets and everything, they would rather rebuild it than fix the stalling only to have another issue develop and generate an angry customer in the process.

Part of the process of being involved in this board is to search the archives as much as you can and then post questions when you get stuck. Undoubtedly, there is much information on carbs in the archives. I learned a whole lot about what I can do now just based on reading things on this forum.

Your oil leak could be a front main seal, which is fixable at home or a rear main seal which requires removing the crank. Check your oil cooler lines for leaks, that can be the death of your engine if they fail. Although, with a 10,000 mile rebuild, it shouldnt be any of those things.
Sometimes the fuel cleaner will cause it to act up as dirt is dissolved. It is accustomed to running the way it is if you know what I mean.


Good Luck

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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

Thanks..yes..I have been reading every single post in the vintage area. What a great website. I am printing items off so that me and some friends (who know more than I do about cars ..thats not hard ) can try to review a few things. These Zenith dual carbs seem to be a usual issue. I put my chances still of slim to solving this myself. Hoping to find a good repair place that is willing to try some things or even better someone who works out of his home.

Sit down and relax a second and have a beer, lemonaide, or whatever. All is not lost.

We know you have a beautiful car; it also sounds like you have one with a good interior and pretty good original paint.
But it sounds like you're (unconsciously perhaps) in the state of mind I was when I bought a nice looking 76 450sl about six months ago. I feel in love with the car, and then got very frustrated to find it had some of the same problems you describe.

I was also told by several mechanics that x, y, and z probably needed work, at huge $$$, and my favorite story is one MB mechanic who suggested a $400 inspection of one issue to see what was wrong (not a repair quote, it was, as he said, "the start of a process." I chose not to begin the process with that particular mechanic.

To make a very long (and in process) story short my car showed tremendous improvement after the basics - cleaning out the old fuel in the tank, replacing fuel & oil filters, the transmission fluid, and a radiator flush.
A couple of bottles of Chevron Techron furl system cleaner, in combination with taking the car on on the highway on a sustained 65mph 1 hr. drive, did wonders.

Now, it still truns out I need a new camshaft to really get this engine running nicely.

But spend some time searching this forum. There are people with LOTS of experience here (I"m not one) and people are helpful.

But you also have to get to the point of accepting that a 35 year-old car is really not at all the same as a modern 2003-5 era car. Actually, new cars today can run really smoothly and easily (for a few years at least).

The fact that your 250 looks great outside can be very seductive. But it is going to need some money, at the very least for a full round of fluids/filters etc service.

The problems you're describing have many possible causes - if you do searches under "idle speed" "starting problems" and such on this forum you'll get a lot of answers.

But you may also still have a good find that has a lot of gunk in the fuel system. Not suprising, even with a recent rebuild, if the car has been sitting around.

So have that beer or whatever, and feel proud of your beautiful car. It's kinda like buying an old house. Things will need replacing and there's probably some hidden rot.

But you know, your car looks way cooler than 99% of anything on the road, IMHO, and you'll find many people agree. Hard to say if you paid too much at $4000, except what does a junky little new car go for - $12,000 - 15,000?

If you're expecting that you can treat your 35 year old car just like a new one, you may be disappointed.

Last serious advice. Don't rush into repairs until you've found a shop you're really comfortable with. Check this forum for recommendations, and learn some of the basic issues with you model.

You may not need a Carb job at all - there's also a thing called Carb cleaner that comes in a can for a few bucks...
Or, you may truly need a Carb job. But I'd try the clean out the system things first, because you have to do them anyway.

thanks for your story. Yes I drank plenty of Bud and did not sleep for a week after this started to happen. You have solid advice. I have already learned alot on the forum...even though I may not be able to utilize it myself...I at least know more of what I am talking about. I keep thinking this carb issue is something small and I am reading everything I can on it so far.

As far as the heat risers go.....it looks like from other posts its ok that they are closed and stuck.

Quoted for emphasis on this part.

All these cars were built for driving. If they sit for a while, stale gas can kill them. Change all the fluids, let the tank run almost empty, then put in a bottle of Techron or another fuel system cleaner (Penzoil worked well for me), and 10 gallons of premium fuel. Change the plugs and the points (if applicable). Take it on a highway cruise, at least 30 mins, with that stuff in the system. Open the throttle often on it (floor it, pass some cars). It's called an "Italian tuneup" and it works wonders.

If you still have issues, start to check for vacuum leaks. The easiest way is to spray carb cleaner around the outside of the carb and manifold and vac lines - any change in idle speed will indicate a leak at that area. Vacuum leaks, old plugs, and fouled points are the top reasons for rough idle and stalling.

We all know you'll love your classic Benz, and you'll learn as you go along. it's a lot easier to work on a car than most people think. Start with simple stuff and work your way up. Plugs and points are easy to do, and a new set could possibly clear up your issues.

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2021 Charger Scat Pack Widebody "Sinabee"
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1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

When the car is cold and I pull off the air cleaner to look at the carb. The furthest choke plate is full open and the other one closest to the front bumber is 3/4 the way or a little more closed. When I close the one closest to the windshield from full open to almost closed is when the car has no problem idle while it is sitting on a cold start.

To turn you into a mechanic, two things are necessary (1) learning how things work and (2) diagnosing what does and doesn't work. You'll get plenty of both here. Lets start with a few observations that don't require any tools, other than a quarter to remove the air cleaner.

There's an ajustment spec for them cold. Hot is real simple, they should point straight up. Also, it's not when the engine's hot, but when the choke heater is hot. With the engine stone cold (some easy in MN according to my Aunt in Sandstone), the flaps should be cold. Turn the ignition on, but don't start the car. You should see the flaps move to the open position in a few minutes.

Don't leave the key on like that for too long, since you're ignition's live. For now, satisfy yourself that they move.

Once you start the car, use a flashlight and look down the throats of each carb. At idle and engine warm, you should just see two dark passages. However, if you see gasoline dripping down one and not the other, the carbs are out of sync or worse. If you see gas from both, then your idle's probably a bit high.

Most definitely replace all fluids and filters. If you don't have a gas filter visible around fuel pump (on the passenger side), add one. Old cars come with rust in the gas tank. It tends to clogg the carbs.

Stalling a bit? Put your hand flat over one carb while you manually kick the throttle. It will feel wet and your hand will get a bit red from the suction, but that's a simple way to draw a lot of gas through the carb quickly. Don't do it often. After doing one carb, wait a moment and do another.

Rarely does this fix the problem, but often it make things a bit better, if the problem is that the car's been sitting with old gas.

Nows a good time to have that second beer.

-CTH

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I couldn't tell from your post if you have another car - sounds like it.

If this one isn't your sole transportation that's another reason to go slow.
I got all stressed out over some of my 450 problems in the beginning until
I "remembered" that I have a reliable, late-model (and boring) alternate.

If you have vacuum leaks from cracked hoses those are really easy to fix. Get new hose and plug in where the old was. My car had a vacuum line completely disconnected for the first month or so and I didn't know.
The "fix" was pushing one end back where it had fallen off.

Have fun!!! You own a classic MB now! Congratulations, you have good taste!

yes..this car was just for weekends and special fun. Its just such a disapointment when you buy something and it worked reasonably well....to making me sweat when I have to come to a light or a stop sign because I watch the oil pressure gauge drop down in the 20's and hear it stall. On the open road everything seems to run fine. I just get sick to my stomach thinking I may have to spend $1200 to get this thing going again. I hope some of the small fixes above work.

use the carb cleaner on the carbs.... all over the outside and insides.. get the pieces moving freely....

if you know how, pull the spark plugs and look at them... any auto manual has pictures of what they should and should not look like...

Light greyish is what you want....

Black is rich...

Oily residue black is bad!

sometimes a super rich mixture will look like oil residue...

If one choke plate is moving and one is stuck open.. it can cause a lean problem during cold driving....... carb cleaner is a quick fix to get these guys moving easily...

another thing to do, is to spray the carb cleaner around the base of the carb while the car is running.. if it changes speed while your duing this, you have a gasket leak... get a new carb gasket and it will solve a super lean condition.. that's like $5...


If carbs are bad, you have choices..I would buy a set of webers before I rebuilt the carbs, but that is me... many guys will disagree with me. It just depends on your philosophy and local smog regulations. I just like their simplicity of repair, tuning, etc... If you go that route, I used JAM engineering in Monterray, CA...or Carmel? he has them preset for MB of your year and type... It's about an hour to 2 hour job.

Good Luck!

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1968 w110 230 Fintail

Take it out on the highway today for that 1/2 hr or 1 hr run, with a bottle of Techron in the gas.
Change the oil right now if you can, or at least make sure the level is right.
Getting the engine above 3000 rpm can really help, as Tomguy said.

But also, re: stalling, you may just need some small engine adjustments.
(idle speed, linkage). A good local MB shop could do those for $100 or less.

And consider this: I've seen mint 250s listed for $15,000 -$20,000. You don't want to throw money at the car, but starting at $4000 you have some room.

Just changed my first fuel filter (stop laughing!) and oil level looks good. I am off for my first Italian tune up on the freeway. After spraying gumout on the carbs they choke butterflys (the top two flaps) still are not looking correct. Back one is still wide open when starting. I will report after Italian tune up.

the one thing that make s me go hmmm? is the fact that the engine supposedly has only 10k on it... if it does it should run like a champ...no leaks... hmmm

fluid checks/changes, plugs and wires inspection, vacuum lines.. are the areas where you should start.. i kind of have a feeling your carbs are not synchrinised though... could be just idle mixture.. is there any type of smoke coming out of the exhaust? what color if any?

also, definately do the italian tune up.. sometimes that will knock things loose and clear up the system.. good luck... any pictures of your sled?

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72 W114/M130

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