Zenith Carb photos - Mercedes-Benz Forum

 
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post #1 of 9 (permalink) Old 09-03-2014, 01:04 PM Thread Starter
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Zenith Carb photos

I've been fighting with the fuel return valve actuating lever for about 2 weeks. This is on a '68 250S. The valve was just replaced from a new OEM, but I think the spring tensioners on mine have been screwed up somewhere along the line. Any photo of the right front side of the front carb would be appreciated.

Jon
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post #2 of 9 (permalink) Old 09-04-2014, 07:40 PM
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these are very tricky. I have been dealing with mine for years and just cant seem to get them right. good luck
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post #3 of 9 (permalink) Old 09-16-2014, 02:25 PM
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here you have a picture
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post #4 of 9 (permalink) Old 09-16-2014, 04:42 PM Thread Starter
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Thanks so much for the photo. My question has to do with the springs on the black lever which operates the fuel return valve (which is not installed on this carb). There is a pin on the "7" or "S" shaped lever just to the left of the black lever. It appears as though you have both of the spring leaves above the pin in this photo. I cannot get the fuel return valve to function correctly with that arrangement.
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post #5 of 9 (permalink) Old 09-16-2014, 11:42 PM
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first check the fuel return valve, it has to move freely, almost with no pressure. Then adjust the springs. Normally they get soft so you have to bend them a little upwards.
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post #6 of 9 (permalink) Old 09-17-2014, 12:13 AM
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I restore these carbs quite often, almost 6 per month, and always same problem with fuel return spring. But 99% of times is the bronze valve, they get rusty inside so the inside valve doesn´t move freely.
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post #7 of 9 (permalink) Old 09-17-2014, 08:27 AM Thread Starter
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Thanks again for your reply. I just replaced the valve with a new one from MB. The old diaphragm was completely torn, and the pin on the bottom was seized with petrified fuel sediment from 15 years of sitting. Even after cleaning and soaking in carb cleaner for days, I wasn't comfortable with the freedom of movement in the pin. The carbs were professionally cleaned and rebuilt, and I have installed an in-line fuel filter just prior to the mechanical pump.

Here a couple of photos of the way mine is set up. I know it's incorrect, but the engine is running very well right now, so I am hesitant to fiddle with it.
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post #8 of 9 (permalink) Old 09-17-2014, 09:24 AM Thread Starter
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post #9 of 9 (permalink) Old 09-20-2014, 01:55 AM
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Normally problem is the pin, I just changed one yesterday to a client with same problem. Pin should be really free. If you push it and feel a little resistance then it´s the pin or the spring inside. Pin should move in and out with no resistance at all.
These valves are installed also on the 32 PAITA and the 34 PICB. I restore all those carbs and I´m use to them.

In any case that valve is installed to avoid vapor lock in the system. Later on a vacuum idle advance valve was installed on the W114 models.

Hope the info helps
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