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  #1  
Old 03-26-2019, 02:18 PM
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Problem. The engine stop only at idle (w111 with zenith carbs)

Hello, I repair the zenith carbs of my 220s with a refubrished kit and adjust them according jaimekop manual. This is the problem I have:

When start the engine at cold (accelerated idle) run perfect at idle and when push tthrotle, but when it warm up (choke flaps full open) at idle stop, only run well when push throttle.

What do you think is the problem? maybe a air leak between carbs and manifold when dissasembled them? I tried to measure the vacuum with a gauge but is impossible because vacuum need to measure at idle, and at idle my car stop
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  #2  
Old 03-27-2019, 10:30 AM
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Idle is set too low?
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Old 03-27-2019, 12:31 PM
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I agree - it sounds like the idle rpm is set too low.
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  #4  
Old 03-27-2019, 01:08 PM
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Quote:
Originally Posted by ScooterABC View Post
Idle is set too low?
How can I increase the idle? Is with the small adjustable linkage in both carbs?
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Old 03-27-2019, 01:22 PM
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Originally Posted by heiwaz View Post
How can I increase the idle? Is with the small adjustable linkage in both carbs?
The linkage does not control the idle and should be disconnected in order to properly adjust idle and balance the carbs. There is going to be a mixture screw that controls how rich the blend is and an idle screw that controls how much fuel comes in when the throttle is not being pressed. The Mercedes manual should document starting points for those screws that should get the car to run. Then you tune the car accordingly and balance the carbs. If you haven't done this then it's not surprising that the car doesn't idle when warm.
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Old 03-27-2019, 01:25 PM
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Quote:
Originally Posted by heiwaz View Post
Hello, I repair the zenith carbs of my 220s with a refubrished kit and adjust them according jaimekop manual.
What is the "jaimekop" manual? You kind of need the Mercedes shop manual to tell you how to adjust the carbs and the linkage. There are very specific instructions that you follow in a particular order.
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  #7  
Old 03-27-2019, 02:46 PM
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Jamie Kopp has provided on his site the Zenith manuals for many years. Pretty much the only place I know on the web to access them.



http://www.jaimekop.com/mb-zenith-carb-manual/

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Old 03-27-2019, 03:35 PM
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Originally Posted by rumb View Post

http://www.jaimekop.com/mb-zenith-carb-manual/
Dead link.
Try http://www.jaimekop.com/CarbManual/index.html
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  #9  
Old 03-27-2019, 04:01 PM
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Generally speaking mixture screws should have an initial adjustment where the screw is gently turned all the way in and then back the screw out 1 1/2 to 2 turns. This is an initial adjustment.
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Old 03-27-2019, 04:03 PM
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Originally Posted by BWhitmore View Post
Generally speaking mixture screws should have an initial adjustment where the screw is gently turned all the way in and then back the screw out 1 1/2 to 2 turns. This is an initial adjustment.
Is there not also an idle screw that has an initial adjustment? I've been away from zeniths for a long time but it seems like every carb is about mixture and idle...
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Old 03-27-2019, 04:15 PM
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Yes, there is an idle adjustment screw. If a freshly rebuilt engine is being started, the idle adjustment screw should be adjusted to achieve around 1000 rpm in order to insure that the cam is run in properly. Only a guess, that the final idle speed should be around 600-700 rpm.
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Old 03-27-2019, 06:53 PM
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I will be very grateful if someone tell me where is the idle adjust screw, because in my carbs only found the air mixture screw (and is adjusted 2 turns, according jaimekop manual). I did a search how to adjust the idle an no found anything. Please need a help
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  #13  
Old 03-28-2019, 11:20 AM
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Jaime Copp's directions are excellent. Better than the MB manual. Some things may be little different because these directions, I think, were originally written for BMWs, which used the 35/40 but were slightly different.
Before you can adjust the Zenith carbs you need to:
- adjust the valves on a cold engine
- set the dwell
- set the timing

The carbs will not come in if these things are wrong. The idle air adjustment should be set at 1 1/2 turns out to begin. You will set the final idle air setting after the throttle plates are set. The bowl vent adjustment is the screw on the top of the carb that touches the lever (some later versions do not have an adjustment for the vent). This is not an idle adjustment. This should be done before the throttle plates.

To adjust the throttle plates remove the linkage between the carbs and the main one from the accelerator linkage. The throttle plates are adjusted with the knurled nut (or 10 MM nut) on the short linkage from the lever to the throttle plate. With the engine warmed up adjust the throttle plates to get the proper idle. You will need to use a Unisyn or similar tool to synchronise the carbs. This can take some time and back and forth. After the carbs are synched you can adjust the idle air screw in each carb to acheive the highest idle. Use a tach/dwell meter. The final step is to adjust the linkage between the carbs. Loosen the nuts on each end and adjust the ball ends so that there is no effort need to connect both carbs. Tighten the nuts and you're done.

By the way, if you think there may be air/vacuum leaks you can spray some carb cleaner in the suspect area with the engine running. If the idle changes there is a leak. If the car is an automatic make sure the vacuum line to the dashpot is not leaking and the dashpot is adjusted right. This can also cause a stall with the car in gear.

Good luck.

Last edited by dobrodan; 03-28-2019 at 07:01 PM.
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  #14  
Old 03-28-2019, 03:08 PM
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some carb kits come with more gaskets for different versions of the carb. The gasket under the top portion of the carb must be exact and the top can't be warped the dealer sells that gasket separate. Some can't be fixed and new Webers wok great. I have fixed many and not been able to fix more. Good luck.
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  #15  
Old 03-30-2019, 04:03 PM
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It has been awhile. Remove the idle passage screw down towards the base of the cab. Assuming you carbs have them. Gas should flow out. In my experience the passage gets filled with dried gas residue. Your carb cleaner may not have cleared them properly.

No gas comes out and I will post how to deal with that easily. When on idle of course it depends on suction. This setup is notorious for old leaking gaskets under the carbs.

I am not that good on these carbs. At the same time if the car ran good the last time before it sat. Or was only infrequently used. Those passages will block.

I developed what I think was an easy way to clean them on the engine. Still use it on small carbs to this day. I used to make up the new gaskets under them as well. Out of what I cannot remember. The thicker one I sometimes padded up with a thinner one to eliminate the air leakage. When these carbs are good I like them.

Laquer Thinner will dissolve built up dried gas residue better than anything I have ever seen. Plus the engine will run on it. It has to be a real chronic problem as even if an engine was running fairly good. A soaking while on the engine almost always seemed to further improve them.

Of all the needless kitting of carbs over the years for this fault really hit home with me. Although you have to use common sense. Yet on idle problems this is the first place to go. Air leaks and obstructed passages. A completely obstructed passage will usually clear in twenty minutes or less. You just watch for the flow to start or improve. If you pull the needle and have good flow first of course you know it is not the problem.

Another indicator of the problem is how far out is the idle screw to start with? Lightly screw it back in to tell. You get a lot of turns of course the likelihood of an air leak or partially obstructed passage is probable.

Last edited by barry12345; 03-30-2019 at 04:36 PM.
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