jerky driving

[Ulfi]

This topic might be covered elsewhere, but I haven't found it yet. The thing is that my 65' 230 SL is very jerky up to 2000 rpm - above that, it's smooth sailing.
It idles well too, the problem only occurs when the engine actually has to move the car. So far we have adjusted the valves, gone though the timing - it even passed a compression test with flying colours.
There is also a slight tapping noise from cylinder 5 which the valve adjustment failed to cure - could this be a related problem?
As spring is approaching the tiny capitol of Denmark, I would be grateful for any ideas (so would my mechanic who was just about to quit smoking when I brought him my Merc....)

Thanks in advance

[jameshoward]

Ulfi,

I don't have any great solutions for you - just suggestions. You say you've done plugs, wires, etc, i.e. everything ignition and valves, etc. I assume you've checked the dwell and then set the timing at 3000rpm as per the book. You should also check the linkage. There is a very comprehensive thread by ja17 (I think it's at the top of the engine section) which you might want to look at if you haven't done so, as there's little point doing anything until you've got the linkage correct. It took me about 3 goes to get mine correct and once I got it the difference was significant (I had a rich/lean problem). You might then check your fuel flow to the FI pump. There's a lot on this site about the flow rate, etc. Basically, there are a load of different things you could look at. Perhaps a few more searches under things like ignition and fuel flow, etc, might throw up some options. If you suspect issues with the valves on cylinder 5 you could worse than to take the car to a garage with a bosch krypton tuner diagnosis thingymabob and see how the valves are functioning. I found that useful and it cost about 15 euros to check.

Good luck.

JH

[paulr]

I had a similar problem and had all the usual suspects changed. I thought that that was it...until the car was put on an analyser which found that the mixture was weak for my engine at 2500rpm. It's all been adjusted throughout the rev range and it's absolutely bl88dy brilliant for the first time it's life.


Try that.

paulr
1970 280 SL

[Ulfi]

Paul & James - thanks for your advice, the timing is set and car has already passed the analyzer with flying colors, the fuel pump in the boot has also been ruled out yesterday (read elsewhere that it was supposed to give 0,8 - 1,3 bar  but if this is the problem, wouldn't the jerky driving also be present above 2000 rpm? ). The linkage is my prime suspect now and I have passed your advices on to my poor mechanic who is also looking for some other kind of analyzing equipment of which there is only one in Denmark - Mercedes Denmark is tracking it down at the moment. Just want to rule out everything before taking the FI pump off and apart as this is ridiculously expensive...(there is actually a used one for sale for a ludicrous €250 at the German eBay (www.ebay.de - search for "einspritzpumpe mercedes pagode" if you're interested...).

[Ulfi]

Could the cold start valve be an issue to be considered in this context by the way?

[rogerh113]

Hello,

If the other work you are doing does not resolve the problem, I would revisit the fuel pump.  When my fuel pump wore to the 'failure' point, the car would die at idle, but if I kept the revs above 2K it ran fine.  Didn't make any sense to me either, but car ran great again when I put in the new fuel pump.......

Regards -- Roger

[Ulfi]

Roger - thanks! I think you've nailed it there as the car works great above 2000 rpm and sometimes dies out all of a sudden when idling (forgot to mention that, sorry). Ulf

[Naj ✝︎]

Hello, Ulf,

You could also check whether you have the correct throttle body to match with the type of distributor you have.

Info is on 'our' wiki:

http://www.sl113.org/wiki/pmwiki.php?n=Fuel.Throttle

http://www.sl113.org/wiki/pmwiki.php?n=Electrical.Distributor


naj

[Ulfi]

DANG! The fuel pump wasn't the issue...

[ja17]

Hello Ulfi,

Sounds like linkage to me!

Joe Alexander
Blacklick, Ohio

[rogerh113]

Hello,

Have you resolved your problem yet??  I would suggest fixing one thing prior to changing something else (like the transmission).  Problem solving is sometimes not so easy, and would be complicated a whole bunch by shifting out the transmission prior to resolving the idle problem.....  Does the engine run ok when it is not under load - when just sitting in the garage not in gear, do you have the same operating problems under 2K rpm??  Have you gone through the linkage setup??

Regards -- Roger

[Ulfi]

Roger: No, I'm still waiting for my car. My mechanic has passed the car on to a specialist who has ordered some gizmo from MB that is needed to adjust the linkage, so hopefully it will be back on the road this week (my wife and I are going to Sweden for a romantic weekend without kids and I would love to take the Pagoda instead of my dull BMW). Fingers crossed....

[Ulfi]

The problem is still not completely solved, but the driving has improved a lot after fiddling with the distributor, the injection pump will be overhauled by a specialist once the season is over, but it is acceptable for now - thanks to you all for your very helpful inputs which I greatly appreciate.
Have a nice summer (to the ones on the northern hemisphere at least...)

Ulf