1966 Mercedes 230S fast idle screw

[PrestonK]

I just bought a 1966 Mercedes 230s, when I start the car the engine stall then shut off. I have to press on the gas for it to stay up running. My friend said it could be the fast idle screw adjustment but we looked for it couldn't find one. Anyone know where its located? I am having hard time adjusting this carburetor.

[gmog220d]

Your car should have a pair of Zenith 35/40INAT carbs, in case you didn't know already. That'll give you something to search by.

Does the engine idle on its own once warmed up?

There is a fast idle adjustment. The screw is located inside the choke heater element housing, and there should be an opening in the side of the circular housing into which you can insert a small screw driver.

But there are other factors involved, like the overall condition of the carbs, idle circuits, etc. Before turning any more screws I'd find and read everything you can about those carbs to orient yourself to them. They are kinda complicated, those INATs. Saw in another thread here on PP that "INAT" stands for "I Need A Tow"!

FWIW, it sounds like you have a basic idle circuit problem to me.

If you have trouble finding the basic specs and procedures let me know. I've got a book that has a fairly good section on the INATs. The good ole Glenn's book (Glenn's Mercedes Benz Repair and Tune-Up Guide by Harold Glenn). You can pick up a copy off eBarf for pretty low dollars.

[PrestonK]

I can see there are hole at the bottom of each heater element, however when I stick a screw driver in the hole, I felt nothing, so I took the cover off on both element and still couldn't find any adjustment screw, the front heater element I found a ring washer felt off, so I screw it back in. Also I notice when I rev the engine the RPM idle stay high, then I rev the engine again the RPM drop to normal idle, then rev again the RPM stay high again doesn't drop the idle, don't know what could be the problem. Also the engine vibrate, and I notice the engine mount is not in a good shape, could be the problem.

I just bought this car for 4 weeks now and been trying to adjust this carb so I can start using it but I have no clue about carburetor adjustment. I am in a learning curve.

I will buy those books you recommends, thanks for the quick reply.

[dobrodan]

Not trying to be harsh, but if you don't know carburetors then you might want to stop turning screws until you do a few other things first. These carbs are very dependent on vacuum, proper valve adjustment and timing. They cannot be adjusted without getting those thing right first. To adjust the carbs you will need a unisyn or similar device. It's critical to get everything adjusted right, including the throttle plates, stop screws, and fuel return. I'm attaching a .pdf manual for the Zenith carb. Thanks Jamie Kopp. The fast idle screw can be seen by opening the throttle completely - not running obviously - and the screw will poke out of the hole, probably in the front carb. Although it sounds like your fast idle is working somewhat already. One quick thing to try is to remove the idle screws and spray carb cleaner into the orifice to clean out the idle circuit. You can test the idle circuit by covering the small hole in the top of the carb next to the main stage opening. A pencil eraser works well for this. If the engine loses RPM then the idle circuit is working.

[muleears]

Originally Posted by PrestonK

I will buy those books you recommends, thanks for the quick reply.

Here's a link to a cheap one:
Glenn's Mercedes Benz Repair Tune Up Guide Paperback | eBay

No affiliation, just trying to help!

[PrestonK]

Thank you very much, i found out one of the cyclinder doesnt hold pressure. Now i need to find a mechanic to fix my bad value..

[strelnik]

Originally Posted by PrestonK

I can see there are hole at the bottom of each heater element, however when I stick a screw driver in the hole, I felt nothing, so I took the cover off on both element and still couldn't find any adjustment screw, the front heater element I found a ring washer felt off, so I screw it back in. Also I notice when I rev the engine the RPM idle stay high, then I rev the engine again the RPM drop to normal idle, then rev again the RPM stay high again doesn't drop the idle, don't know what could be the problem. Also the engine vibrate, and I notice the engine mount is not in a good shape, could be the problem.

I just bought this car for 4 weeks now and been trying to adjust this carb so I can start using it but I have no clue about carburetor adjustment. I am in a learning curve.

I will buy those books you recommends, thanks for the quick reply.

The glenn book is good and the FSM is available cheap. Plus bmw uses these carbs too. I might even have rebuild kits from when I owned a 67 230s, have to see.

[strelnik]

Originally Posted by dobrodan

Not trying to be harsh, but if you don't know carburetors then you might want to stop turning screws until you do a few other things first. These carbs are very dependent on vacuum, proper valve adjustment and timing. They cannot be adjusted without getting those thing right first. To adjust the carbs you will need a unisyn or similar device. It's critical to get everything adjusted right, including the throttle plates, stop screws, and fuel return. I'm attaching a .pdf manual for the Zenith carb. Thanks Jamie Kopp. The fast idle screw can be seen by opening the throttle completely - not running obviously - and the screw will poke out of the hole, probably in the front carb. Although it sounds like your fast idle is working somewhat already. One quick thing to try is to remove the idle screws and spray carb cleaner into the orifice to clean out the idle circuit. You can test the idle circuit by covering the small hole in the top of the carb next to the main stage opening. A pencil eraser works well for this. If the engine loses RPM then the idle circuit is working.

Synchronisers are available on Ebay, just got one for 18 bucks plus shipping.