Zenith Carb issue.

[Ruman999]

I purchased a '69 Mercedes 250. It wouldn't start, but would sputter when gas was put into the intake. I purchased a set of zenith carbs off ebay, and rebuild kits. I put in the carbs I got, just to see what would happen. The car started, but wouldn't idle, but would run okay with my foot on the gas.

I then rebuilt the carbs that were in the car, using the ones I bought as a "guide" as it's my first rebuild. Got these new carbs in, and when I start it, it revs so high I shut the car off after a few seconds. It seems like it's WOT. After messing around with it for awhile, I got it to idle, but just very high. I don't know the RPMs. It may have been considered warmed up, as I had started it quite a few times by then trying to see what would happen.

I could see my rebuild not being perfect, but the intakes are not stuck open or anything, so I'm not sure what else it could be.... any ideas on what to try?

[wbain5280]

Useful Vintage Links at the top of the forum:

Useful Vintage Links

do a find on 'zenith' and click on the link.

[todds]

Well, the air is getting in there SOMEhow if not past the throttle valves. It's a massive vacuum leak somewhere causing it. Could be carb bases, carb itself, a huge imbalance between the two carbs and so on. If you swap back the other carbs does it rectify it? If they are working properly they will have no problem at all stalling the car out due to an idle setting that is too low. (In other words you should never have to "work" to achieve a low idle) BTW this link is invaluable when it comes to setting up these carbs:

http://www.jaimekop.com/CarbManual/

You're sure it's not the vacuum dashpot on the rear carb goosing the throttle too much on initial start? Try screwing it in to the point where it will not contact even with the vacuum hose unplugged and the port stopped off to take it out of the picture. You will want this thing working right though eventually. It allows you to set a nice low smooth idle while preventing stalling/jerking when shifting into gear and on hwy offramps.

[Ruman999]

Well i did find out what it was.. the butterfly flap(sorry not a technical term I'm sure) on the primary carb doesn't shut all of the way after you let off the accelerator. The arm doesn't snap back into place, closing it... I did get it to idle(albeit still high, but not sounding like WOT).

Also, fuel leaks out of the second gasket down on the rear carb, and fuel also leaks out of the fuel return pin. I did see the spring adjustment here on the jaimekop carb site, so I will try that.

I am going to play around with that some more, but another issue I ran into that worries me, and I believe I need to address first, is that when I put the car into gear(foot still on the brake) or turn the steering wheel, the car dies. Basically any load kills it. Any ideas there?

Edit: Perhaps this is what you were talking about with the dashpot and stalling in gear. The vaccum line doesn't go on very well, and I'm sure it's leaking a bit. I hadn't fixed that yet because I didn't think it'd affect me until I actually got to be able to move the car.

[Ruman999]

Well it's idling high again. If I keep the top choke closed, so it's only pulling air from the back carb, it idles okay, but if i just crack the front carb, it accelerates very high.