misfiring, or stumbling or whatever

[n/a]

 :?:  Here's a perplexing problem that has surfaced with my 280SL (1969 4 spd). When I first got the car, I noticed that it hesitated, or misfired or stumbled- a feeling like the engine was missing or not firing on all six cylinders, especially under load, especially at part-throttle in top gear (which is one of the higher loads the engine has to bear in any car). The car has been in for a comprehensive service, which included a complete ignition tuneup, setting the valves, setting the FI system and setting up the engine on a gas analyzer. The technicians who did it are Mercedes trained and old- they recall these cars when new. They also road-tested the car, but clearly not for long enough, as the car was driven today by one of my friends who confirmed that it does stumble, or miss, or whatever you want to call it. Here's my question: has anyone else had a problem like this with their M180 engine 113 car, and was it solved, and if so, what did it turn out to be? I am not keen on the idea of replacing parts until the problem decides to go away- some of the parts that might be culpable, such as the ballast resistor and coil, are cheap. Some, like the FI pump unit, are not. In the meantime, I feel behind the  :?: .

[Jonny B]

There are a multitude of possibilities here. Have you searched through the previous posts, as this appears to be a relatively common problem. There are a lot of areas discussed as to what might be the problem (fuel flow, filters, injectors, etc., etc.). You may find a past item that helps point you in a more narrow direction. P.S. mine turned out to be fuel tank junk, fuel pump worn, and mis-adjustment of the idle set up.

Jonny B
1967 250SL Auto

[George Davis]

Ditto Jonny.  Look inside the fuel tank for rust and loose crud that may clog the pickup.  There is also a screen in the fuel pump inlet fitting that could be clogged.

A fairly common problem that causes poor running is a blocked fuel return line.  Have the entire return line checked for free flow, especially the part inside the fuel tank.  While they're at it, check the fuel delivery rate from the return line where it connects to the tank, should be at least 1 liter in 15 seconds.

Good luck!

George Davis
'69 280 SL Euro manual

[Richard Madison]

Jim:

After arriving at the recent gathering at Tom Sargeant's Virginia spread, my 1971 began to stumble and misfire...and a near backfire once in a while. This was not a bucking or deep stumble, more like the rhythm of the engine was not steady even at speed. Had the car for two years with no previous problems...

Luckily, I was surrounded by helpful Pagoda experts and had access to Tom's very complete workshop garage and lift.

Turned out to be the points gap...the gap (due to wear?) had virtually disappeared...one of the attending experts (doesn't even own a Pagoda) worked for about an hour setting the gap as near to spec as possible using his eye, a feeler gauge, and re-set the dwell using a dwell meter. (Tom had everything we asked for).

Drove the car back to NYC, 250 miles...smooth and steady...
At least in my case, the stutter was from the points gap or the dwell...
Richard M

[ja17]

Hello Jim,
Yes many possible causes. As George implies, a good clean and ample fuel supply is a must. Dirt or contamination may be clogging the system after running for a while. You will find signs of this contamination in the fuel filter and possibly blockage at the screen in the electric fuel pump intake. On the other hand, I have seen a bad coil or condenser cause the same symptoms after heating up. Yes points also will also give these symptoms, however we may assume these were changed with new, when the work was performed. New points sometimes "settle in" after running a while. You may want to re-check the dwell before digging in further also. Good luck. Keep us posted.

Joe Alexander
Blacklick, Ohio

[gwuisman]

I had a simulaer problem this summer after the garage had serviced the car. By trial I discovered that the (new) first piston did not function well. After replacing the problem was gone.

gwuisman
1970 280sl

[n/a]

Thanks to all, we are still trying to figure this out. The car is going back to Euro Monday AM and we will test drive it again...they already changed the fuel filter. I don't know if these cars have a tank filter as well. They did not replace the spark coil or the ballast resistor, which I believe can cause problems of this kind. The CO was set and is within spec. The problem appears to occur more at part-throttle high load- 1500-2800 revs in top gear. We will see what occurs Monday, and definitely I will post progress and when we find out what it is, so someone else may benefit.

[n/a]

Here's an update, of sorts...the fuel supply is clean and appears flow is adequate as well. The plugs looked a little hot, so we put in a slightly cooler set of Bosch plugs. On diagnostic scope car looks fine. Tuesday AM it gets a new coil and ballast resistor- we'll see what that does. If that does not improve things, I've agreed we will take the FI unit and nozzles out and send them off to be overhauled and calibrated. Film at eleven, as they say...

[Malc]

Jim,
Don't forget to check that the ignition timing is right...changing plugs sounds abit suspect...
Even if the timing has been set statically (spelling??) It should be checked dynamically to ensure that the distributor weights are moving on the correct advance curve, also check you have no air leaks especially on the intake side of the engine, hoses fallen off, split etc
These checks are cheap and easy to do with a reasonable engine analyser before diving into the fuel pump. A mate who works for the RAC (Royal Automobile Club) told me that 95% of car problems are ignition related, even modern cars....
Good luck
Malc

[n/a]

Here's the latest, regrettably not good news...we have been entirely through the ignition system including the coil, ballast resistor, distributor out, etc- the problem is not in there. Euro attempted to reset the injector pump feeling that the problem was a lean misfire (the CO dropped when the engine was revved) and the engine now runs worse than before.
  Although the guys at Euro are friends of mine and I like them a lot, I have decided to withdraw the car from their care entirely and try someone else. At this point the car is stashed away waiting its' turn in line to get into another shop. I think the problem is in the FI either in the pump or in the nozzles. Very likely we will end up rebuilding both.
  That said, it is a really beautiful example of an SL and this could happen with any old car, so I am just slogging through the process hoping there's light at the end of the tunnel. I do feel, at this point, that a contemporary MB dealer service shop, no matter how nice they are or motivated, doesn't have much to contribute on older MB cars. They just don't see them enough, although they tried hard.

[Cees Klumper]

Sorry to hear about your trials and tribulations. When I first got my '69 280 SL automatic, it had erratic stalling problems and after MUCH diagnosis by several specialized shops (one not so specialized as the other) the problem turned out to be an incorrect-type distributor for the engine (retard vs advance or vice-versa, can't recall). This caused the idle CO to be much too high causing the car to stall at traffic lights etc. Then last year I had an ignition problem again, misfiring at higher RPM's and it turned out to be the ignition wires (only two years old). But, by and large, once these cars are properly sorted they generally do go on without problems for long periods of time. It's that initial "sorting out" that can be frustrating. No substitute for the mechanic's/shop's experience in that department, with all of those little things that can cause big problems. Good luck,

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[rwmastel]

quote:...so I am just slogging through the process...

Jim,
I hope their process is a sound one!  I agree.  I would never take my 37 year old SL to a MB Dealership.  At least, not the ones around here.  When I take my E420 in for service, I look around and never see anything older than 10 or 15 years in the service area or on the used car lot.  Find a good specialist and learn as much as you can yourself so you can effectively communicate with them.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[Douglas]

Jim, I just got a call from H&R Fuel Injection informing me that my car is ready. You might say I've been waiting years for that call because I've suffered from similar gremlins to yours. And like you, I replaced all the typical culprits, but to no avail. We'll see what they did, but I can already tell you that I have a better feeling about Hans just based on his known expertise.

Douglas Kim
New York, NY
280 SL #018260

[n/a]

Doug, I agree. I hope your car is straightened out, and I agree with Cees that once these cars are dialed in they run fine- I am old enough to have bought them new and I recall the M180 engine running perfectly when new. Hopefully this one can do that. I suspect the injector nozzles or pipes, or both. However, if the FI pump has to go in for a rebuild, we'll do that too.
  I should mention in fairness that Euro did a lot of other things besides the engine work- changed all the fluids, got the A/C working (such a comfort in November) and did the flex disc and tightened the transmission output flange which was loose. I put in the Koni shocks and changed the diff mount, with help from friends. It's only the engine which they really weren't able to improve. Well, no one's perfect- even at a price which implies perfection.

[Ben]

Isn't it normal for the mixture to lean out at higher RPM ? I think that once the pump is set correctly you dont ever need to touch it except for idle adjustments !

Regards,
Ben in Ireland.
'64 230SL 4sp.
'03 CLK Kompressor

[France]

Jim,

Sorry for chiming in late, but we had the same problem with my 280SL when it arrived in FL.  Thomas traced it to a too-rich fuel injection pump setting.  It had fouled all of the intake so was only cured after taking all of the intake parts apart and cleaning them.  In other words, just changing the setting without cleaning the intake will not help.  She runs great now, and it took about 4 hours of work.  Hope you are sorted soon...

Best regards,
Trice

Trice
1968 280SL US, signal/bl leather, auto

[n/a]

Some progress, possibly...brought the car to a friend experienced with MFI cars; he reports that the ignition timing was set at zero degrees, and that reset at twelve BTDC the car runs perfectly. We'll see, I guess...I haven't driven it yet. I can't find the spec for a 1969 manual-transmission 280SL timing. If anyone else has anything on this, I'd love to hear it...

[Tom]

Jim,

At my home, we checked your timing and as I recall it was very much within spec.  You were having the hesitation at that time so it seems strange that timing could have shifted and now causes your problem.

I think you have the 051 distributor, which has timing spec'd at 30 BTDC at 3000 rpm (with out vacuum), 12-19 BTDC at 1500 RPM (without Vacuum) and 3 degrees ATDC (+-1) with our without vacuum at idle (800rpm)

Keep us posted, however should the timing adjustment solve the issue.  12 BTDC seems pretty far advanced-I don't recall that being spec and I suspect you will have an idle problem at the setting.

Best,

Tom

[n/a]

Tom, I agree and no one is more puzzled or frustrated than me on this. However, the car went to Randy Rodman at Auto Shoppe in Maryland, and he felt that the timing was the issue. I am going to test drive it tomorrow. We'll see. I am a firm proponent of having things set the way the factory intended; I take it as an article of faith that MB cars come from the factory well-sorted-out. They wouldn't have sold forty or fifty thousand 113 cars is they all had run like mine does now...but performance is the acid test. In the last analysis, results are what counts.
  Film at eleven, as they say, or 'watch this space for further details'...

[Douglas]

Hans of H&R tells me my car is now purring, so I'm itching to get out to Bohemia on Saturday morning to pick it up. Similar symptoms to yours. Hans tells me the air and pump adjustments were out of sync. He described the pump as running behind and not enriching the mixture enough as more air was introduced. He tweaked the setting for the air at idle as well as the idle speed.

Douglas Kim
New York, NY
280 SL #018260

[n/a]

Well, here's what happened: Auto Shoppe of Silver Spring examined the car and discovered that the timing was set at zero degrees. It was reset to 12-13 advanced and the engine is transformed. The car runs dramatically better and is as far as I can tell running as it ought to.
   I have no explanation whatever for the fact that the mechanics at Euro Motorcars set the engine to what is supposed to be 'factory spec' and it ran badly, then it is advanced to what is not 'factory spec' and runs great. Maybe this depends on how it is meaasured, or where you get your specs- I have no idea. What is disturbing to me is that essentially Euro didn't believe there was anything wrong with the engine, despite it being driven by THREE knowledgeable people (inc one Forum member) who felt that it did not run right. It is as if they were willing to keep screwing around with it at 90$/hr even though they weren't able to tell it ran poorly.
   Total bill from Euro: $3400  Total bill from Auto Shoppe in Silver Spring: $110.
   I cannot think of a circumstance in which I would be willing again to take a car to a dealer service shop. This experience has confirmed all my worst suspicions about dealer service: expensive per hour, condescending attitude,  glitzy shop but no expertise on a vintage car, an absolute unwillingness to admit that anything is wrong- the end result a furious customer who would rather sell the car than go back there if there were no other choice. Fortunately, there is.
   It's fair to point out that Euro did some other things, and that they appear to have been done competently. (change fluids, new A/C hose and evacuate and charge system, r/r radiator and boil out, tighten transmission output flange, put in flex disc, repack bearings along with comprehensive greasing etc. But all that at a reasonable shop would have cost maybe $1500-1800. (I supplied some of the parts, by the way). The second visit, where they attempted to address the engine running issue, was a total failure and cost $700. I did, however, get a new coil and ballast out of it, so it is not a total waste.
   The take-home message, as one of my professors used to say...? Stay scrupulously away from MB dealers unless you have a new MB car UNDER WARRANTY. When the warranty expires, find a good independent service shop and stick with them. I have learnt my lesson- in spades.[!]

[Cees Klumper]

Congratulations Jim - I know just how it feels to get the car back in proper running order, after such an ordeal. And no, current-day Mercedes dealers do not have the knowledge and experience necessary to work on these cars, but can we blame them. We CAN blame them for pretending though. And then there are so-called experts at the vintage cars who don´t know nearly enough either. So this is why I have come to the point of being able to do most (not all) things myself, essentially learning from all of the generous advice and information on this and its predecessor (Yahoo!) sites from many different people, Joe Alexander and Dan Caron being the most outstanding. The only other alternative is a good shop (capable, dependable, fair).

Cees Klumper in Amsterdam
'69 white 280 SL automatic