71 280s Stalling Problems

[71 280s]

Hello,
This is my first post here, given that I just bought my 1971 280s (automatic) last week. I have searched through the site for a similar problem, but cannot find such a detail.
When I tried to start the car a couple of mornings ago, after I shifted from Park to Reverse and then released the brake, the engine idle plummeted and then stalled. I tried a few times in Reverse and Drive with the same result - nice idle in Park, stall in any other gear (didn't try neutral). I was able to get out of the parking lot by riding the brakes - keeping the idle up by depressing the accelerator as I released the brake. Since then I have had no problems. Living in the S.F. Bay Area and being in next to the water that morning under cover of fog the temperature was probably in the 60's.
I called a recommended service centre, All Mercedes, and he said to get rid of it while I can, that it is probably a carburator problem. I feel that he is overreacting and that the problem is probably more simple than that.


Thank-you.

[Mark DiSilvestro]

It could be a carburetor problem but I would never get rid of a Mercedes simply for that. Typically, with these carbs, If the engine is cold, you need to pump the accelerator two or three times to set the automatic chokes, then take your foot off the accelerator before cranking. At this point, if you were to remove the air cleaner lid, you should see that the choke flap on top of each carburetor is closed. After it starts, it should run at a fast idle until you start to drive it and warm it up. There are adjustments to the choke and fast idle that should be no problem for a mechanic with carburetor experience. Also vacuum leaks and point gap/ignition timing can affect cold starting. You said its been OK lately. Perhaps you were unfamiliar with starting a cold carbureted engine or a choke was temporarily stuck open.

Happy Motoring, Mark

[pj67coll]

That mechanic is an idiot. My first Mercedes was a 71 280S. A wonderful car. Just get the carbs running right and enjoy it. Only thing to watch for is rust. My steering column snapped because the steering gear box had started moving around as the chassis box section it was mounted to had developed severe rust. I was in Durban, South Africa. One of the worst rust climates on the planet. SF may not be as bad, but anywhere near the sea would cause me to be careful on that score. Check out Jaimekop.com for dual Zenith Carbureattor manuals.

- Peter.

[JMela]

he said to get rid of it while I can.

That's a funny line.



I've got a 68 280s that I really enjoy. Maybe this killing problem would be lessened with an a longer warm up period.

To echo what the others have said, find an old-school Euro tech who is comfortable with these Zenith carbs. Difficult to set up, but they run well when dialed in. They need to be synched perfectly or strange behavior results.

Let us know of any further questions - the archives here are a great resouce as well.

[mzsmbs]

vacuum and fuel filter could be what needs changing...

[71 280s]

Having started my 280s many times in the past week during similar conditions, I think it is I that has been the problem, and not the car. As a couple of posts have stated, I think it has been my unfamiliarity starting the non fuel-injected vechicle that has been the culprit. I notice that when the temperature is hot, or the car has recently been running, I don't need to pump the accelerator at all, but if it is first thing in the chilly morn - I need to pump a couple of times. A close reading of my drivers manual echoed much of the advice on starting received here. Thank-you. I have a couple of other questions, but I'll start a new thread for that.

[pj67coll]

That's great news. I remember mine as having similar charachteristics. When cold I'd have to depress the accelerator to the floor once or sometimes twice and then keep it depressed about a quarter of the way down when cranking. Usually fired up within the first or second turn of the motor.

When hot, I seldom had to touch the pedal, and the thing would fire up the instant I applied pressure to the key. It was so quick it was almost subliminal.

- Peter.

[cth350]

Now's a great time to drive the car around until you find a shop that works on older mercedes and BMWs. A porche mechanic will do fine too. Have them look at the car and check out the carbs just so they're familiar with the vehicle. This is VERY cheap insurance for when you find yourself needing a mechanic.

-CTH

[71 280s]

Hey CTH,
That's what I'm trying to do right now, but I haven't had a whole lot of luck. I've been looking through the suggested posts here, but no good luck yet. I had the tires replaced today - the ride is much better. I'm having an intermittent overheating problem, but I think I can figure it out from past posts on this forum. Anything special in an oil/oil filter change I should know?

San Fran East Bay


Thanks.

[JMela]

Originally Posted by 71 280s

Anything special in an oil/oil filter change I should know?

You want to drain the oil cooler as well as the pan. Cooler is located next to the radiator with a drain plug on the bottom. Replace crush washers on both pan and cooler drain plugs - they're included in most quality (Hengst, Mann, MB) filter kits.

There's three rubber bushings not included with your standard oil filter kit. They are necessary for proper filter seating/ function and are usually missing or in poor condition.

Part Numbers (from your MB dealer) are:

#53 is 000 184 1780.
#52 is 000 184 3280
#2 is 000 184 3380

[Mark DiSilvestro]

I run 20W50 convetional oil year-round in my high-mileage 220S '60 Fintail and change it more often than my modern car, but I rarely drive it in severly cold weather. You may be OK with 10W40 year-round or 20W50 in summer, then 10W40 for winter.
In the bottom of the oil filter cannister and where the cannister mounts to the engine, there should be a 1.5 inch diameter rubber oil seal ring for each end of the filter. Sometimes, after many years of oil changes, one of them will 'disappear', rendering the oil filter ineffective. When you change the filter, make sure they are still there or you'll probably need to order them. It may be a good idea to go ahead and get them anyway, just in case. You should always replace the 3-inch diameter 'O' ring cannister gasket. Usually a new one comes with the new oil filter.

Speaking of 'mechanics' and 'faulty carbs', in 1995, I met my Fintail's original owner through a mutual friend. That owner, an eldery lady, called me up out of the blue one afternoon, in near panic. The Mercedes had developed a bad fuel leak and her Mercedes mechanic was telling her she needed new carburetors and, if they could find replacements, it was going to cost thousands of $$$$! I went over to her home to have a look and it took a whole minute to tighten the loose fuel line fitting at #1 carburetor. Over the next few years, I helped her out of other car problems when I could. When she passed away in 2001, she left the car to me.
Those 'faulty carbs' are still on the car today!

Happy Motoring, Mark

[MrCjames]

Vintage MBs required more tinkering than the late model vehicles, simple fact. I was in Maryland a few months back conducting a technical class but before I went I had made arrangements to visit with a repair shop that was having difficulties with a 1968 or 69 250SL. The majority of staff in the shop are younger than 35 and they have little to no interest in trying to understand older mechanical wonders. After spending 4.5 hours with the vehicle I had it humming a new tune. I rebuilt the distributor, reset all the throttle linkage, cleaned the throttle plate, adjusted the throttle contact switch, corrected the auxiliary air setting (thermostat on injection pump), changed the engine oil and filter, installed new plugs, set the dwell and timing, adjusted the CO and then drove the hell out of it.

After everything was said and done we were sitting around joking about various things and all of sudden the shop owner asked me how much I was going to charge for the assistance. I thought about it for a moment and responded jokingly with "just advise the vehicle owner that there are a number of people in this country that possess the skills to repair his car but there is only three of them that truly want to. Those 3 people live in California and they are expensive!" We all got a good a laugh out of it and then headed out for dinner.

Having great appreciation for the mechanical genius that crafted vintage German machinery it gave me great pleasure to tinker with it for 4.5 hours.

[230/8]

71 280S:

If you will search this site for "zenith+carburetors", and 230/8+zenith" you will find several, I hope, helpful threads on living with and caring for your trusty Zenith carburetors. These are some very delightful carburetors for the person who likes to DIY with old machinery. They are often badly adjusted and more often they are replaced simply because the mechanic lacks the skill and knowledge of basic principles to deal with them.

If you want someone to maintain them for you, search for a MB mechanic with lots of gray hair, this may not necessarily be an old mechanic because working on Zeniths has caused many young mechanics to turn gray. If a MB mechanic is not around, look for a BMW mechanic. The Zeniths were used on BMWs in the seventies, the Bavaria as I recall.

As to your current problem, there are several small things you can do yourself. Take a spray carb cleaner and thoroughly clean the choke linkages front and rear. With the air filter lid off and engine cold, check that the chokes close properly. Check that they are set to proper tightness by examining the index marks on the cover and housing. The rear choke on US versions often has a lighter spring so it may be lazy in closing. Fast idle is usually set with a single screw in the front choke housing. The rear choke may not even have a fast idle screw installed, but the linkage will have a provision for it, so if a screw is not there, don't be alarmed. Also, you will probably need to examine the choke access port with a mirror and light to see the screw, which swings into your field of vision only after the choke closes when it is cold. Remember, they are electric chokes so if you forget and turn on the iginition, the chokes will heat and begin to open. This is also something you should check for proper function after the basic cold settings are verified.

There are bunches of settings and adjustments that can be made. I would strongly recommend that, except for what I mentioned above, you avoid casual tinkering with adjustments until you have gained a resonable understanding of what you are dealing with. Some settings are made at the factory and don't need to be changed, ever. Get a good manual, the factory CD ROM would be a good place to start, and the much maligned Chilton and Haynes are actually pretty good for beginners.

Another thing you can do is to ensure the manifold heat valves are functioning. They may be rusted shut and stuck either on or off. Either would be bad for your engine running. Free them up with liquid wrench when the engine is cold.

Finally, take another quick look at your factory operating manual so you are certain of the correct starting procedures. I have worked on my Zeniths for over 30 years and I still learn something new each time I go under the hood.

Keep us informed of your progress. Based on your results, there may be other suggestions and helpful hints this forum's members can offer.

Good luck,

230/8
p.s.:

You should also remember, although the Zeniths are a common source of dirveability problems, it is very common for a symptom (ie hesitation or stumble or stalling) to be shared by carburetor and ignition systems. Make sure the ignition system is in good shape.

[ctaylor738]

I have spent a lot of time on these Zeniths.

A real problem with these carbs is that as they age, they get worn or damaged in areas that can't be repaired. Like warped top plates, cooked by the sticking heat risers. Or worn throttle shaft bushings or seals, caused by 30 years of opening and closing the throttles. Once problems like these happen, if is very hard to get the engine to run acceptably.

There are no parts available commercially to fix these problems, and it's unrealistic to expect a normal shop to search the web for used carbs or cross check o-rings to find the right seal.

If you are going to have a car like this, it's up to you to educate yourself on problems like this, and possilby build a supply of parts that can help a good mechanic deal with problems.

[71 280s]

Hey 230/8

Get a good manual, the factory CD ROM would be a good place to start,



Where can I obtain this factory CD ROM?