Author Topic: Carbs' saga  (Read 3421 times)

Ancedes

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Carbs' saga
« on: April 26, 2014, 12:26:15 »
I own a 1967 sedan 230 with Zenith carbs. I rebuilt them this winter, but I had still the following problem: idle is at 3000 rpm. If I try to lower it, engine died.
Tired of this condition, I bought the K245 Weber kit and installed it. Same problem, high idle and engine dies after 20 seconds if I do not pump hardly the gas pedal. Vacuum line to brake booster is not leaking and ignition advance at 3000 rpm is 38 degree.
Any hint will be appreciated.

ja17

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Re: Carbs' saga
« Reply #1 on: April 26, 2014, 14:11:43 »
Hello Ancedes,

Most problems with these complex carbs is that they are not set-up correctly. When set up correctly these carbs are very dependable and trouble free. The factory procedure is about 12 pages long. I can send you a PDFA of the set-up if you do not have it. In fact your 1967 vintage Zeniths are some of the best, because they add a lot of emission devices on the later versions.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Ancedes

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Re: Carbs' saga
« Reply #2 on: April 26, 2014, 14:19:46 »
I have the Zenith earlier version with near nothing about emission control, which I appreciate, being less complicated to adjust. I have all info about Zeniths, but near nothing about Webers actually on the engine.

ja17

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Re: Carbs' saga
« Reply #3 on: April 27, 2014, 22:38:30 »
Ok, you say you have Zeniiths on your engine in the first post and yo say you  have Webers on  your engine in the last post. Please let us know exactly what you have on your engine. ?
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback

Ancedes

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Re: Carbs' saga
« Reply #4 on: April 28, 2014, 12:59:18 »
The second paragraph of my first post tells that I bought Webers and installed them, but still having the same idle problems. This leads me to believe that the carbs are not the problem. Because the engine dies after 10 or 15 seconds, probably the gas pump is not working properly. I have both the mechanical and electric pumps in series and I get gas to the carbs. Weber's instructions specify 2 PSI pump pressure, which is not a lot.
I will check the plugs today to see the combustion condition for each cylinder.
After a short warm up, I checked the plugs and found them in good condition, slightly beige- brown.
After reading the instructions from Redline, I saw that there was a discrepancy between their sketch and the description. The drawing shows to pipe the overflow fuel lines  to the tank, but they say to cap them. I will plug them to notice if there is any difference on the idle.
To follow!
« Last Edit: April 28, 2014, 19:18:58 by Ancedes »

Ancedes

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Re: Carbs' saga
« Reply #5 on: April 28, 2014, 21:26:29 »
With the overflow return line removed, the engine runs steadily with fast throttle acceleration. 
The only thing to adjust now is the idle.

ja17

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Re: Carbs' saga
« Reply #6 on: April 30, 2014, 04:22:22 »
You should be able to find plenty of information about adjusting the Webers.  In general, move the mixture screws in one at time, when the rpms begin to lower back off the mixture screw slowely, untill the rpms stop increasing. Move the screw and addition 1/8 turn out. Move to the other carb and  follow the same procedure. After this mixture adjustment, if the rpms are too hight or too low, move the carb idle screws  to lower or increase the idle as desired. Now repeat the mixture adjustment procedure again.
Joe Alexander
Blacklick, Ohio
1969 Dark Olive 280SL
2002 ML55 AMG (tow vehicle)
2002 SLK32 AMG (350 hp)
1963 404 Mercedes Unimog (Swedish Army)
1989 flu419 Mercedes Unimog (US Army)
1998 E430
1974 450SLC Rally
1965 220SE Finback