Help 230S Zenith Carbs leaking from Float Valve

[roehlerich]

Hi,

I just came home with a 68 230S. She drove fine. She was registered by the previous owner who died. I bought it at an auction. She has rust but was running well. Now I just fired her up and noticed that gasoline was shooting out from the float valve on the front carb when in idle. She then dies. This did not happen a week ago when I drove her home. Any ideas???? Please???
Thanks, Ralf

[Mike D]

Is it the float valve or the fuel return diaphragm fitting (a large "banjo" bolt screwed into the carb top plate)?

If it's the return fitting, they can be CAREFULLY cleaned and the gaskets replaced.

[roehlerich]

It is from the float valve. It is a spring loaded screw at the underside of the carb that gets released when the throttle is pushed.

[Mike D]

I'm not very familiar with the Zenith's but on the Solex's that is the accellerator pump.

[todds]

I think you are talking about the fuel return valve. It is supposed to circulate fuel back to the tank to keep it cool in the lines when the throttle is released. Later cars just had a simpler small pinhole orifice instead of a valve. Somebody on this list was successful in just plugging theirs up and not running a fuel return. The same thing happened to my zeniths before I ditched them for webers, which call for elimination of the fuel return. I am having hot start issues now.

Perhaps you can locate the orifice fitting from a later car with zeniths and use that, or you might be successful by just plugging up your leaking valve. At any rate the thing simply unscrews with a regular metric wrench. An exact replacement from mercedes is likely available but probably ridiculously expensive. These things probably leak once they start seeing fuel again after being gummed up from lack of use, the same thing happened to me.

If it is your float bowl venting valve instead, then I can't help ya. I'm not sure why gas would be coming out, it is supposed to be just vapor. My float vent valves were always wet too for some reason.

[roehlerich]

It is the float vent valve for sure. I am wondering why so much fuel is building up. Could the return line be clogged?

[nhdoc]

What you are describing is the bowl vent and mine did the same thing. I landed up switching over to webers but before I did I dod some tinkering but am not sure I ever fixed it or knew why it did that. There is an adjustment for that vent which is supposed to be set at idle. You bend the arm so the vent is pressed up by 3mm...you might want to check this setting first.

[roehlerich]

Yes,

I read about that adjustment too. The spring is depressed (pushed upwards) when idling. The question is: Why did this start now? The car ran fine all the way home two weeks ago? I will see how much the valve is being depressed.

[nhdoc]

Originally Posted by roehlerich

Yes,

I read about that adjustment too. The spring is depressed (pushed upwards) when idling. The question is: Why did this start now? The car ran fine all the way home two weeks ago? I will see how much the valve is being depressed.

Mine did the same thing, only my car for whatever reason never had a fuel return line. Also, I had just replaced the pump with a new one which may have been delivering pressure in excess of my old one and overpowered the float valve...at least that is my theory. I installed weber carbs and a pressure regulator to keep the feed pressure below 3 PSI and now all is well with mine. I fought with those Zeniths for 2 years before surrenduring.

You may want to check your return valve and make sure it is operating properly...it acts essentially as a pressure regulator if I understand its design properly so if it is restricted or stuck you could have the same overflow as I suspect mine had.

[roehlerich]

Thanks Marty. Will do.