280S gas how to bypass emission switches - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 07-13-2011, 12:17 PM Thread Starter
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280S gas how to bypass emission switches

I have queried this forum several times with no response. I am becoming desperate in my attempt to get my 1771 280 S running. I have lost my job and will need to use her as my daily driver.
Problem: will not idle below 1100 RPM
• Both zenith carbs have been professionally rebuilt
• Ignition upgraded to Hot Point 50K
• Fuel system flushed
• I have one idle solenoid that does not work but it has already had the end clipped off anyhow.

I do not know how the emission switches should be hooked up and I want to return the car to euro status. The instructions I read says to attach the rear carb to the dashpot but I do not have dash pots on my carbs.
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post #2 of 3 (permalink) Old 07-13-2011, 02:26 PM
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Before you let yourself get al frazzled, take a step back and breathe a little. It's something I've found that works when chasing carb problems. After a few deep breaths (and possibly a few beers), try to get your head around how the system works. If you understand what it's supposed to do, you can figure out why it's not working and what is not working.

You may have to take a trip to the public library to get some reading material, but it's a nice place to get info for little to nothing. Many Libraries have subscriptions to AllData or Mitchell OnLine, and you may get a complete wiring or vacuum diagram printed out for 10 cents a page. Oddly, a lot of people forget about them, in this age of the internet.

If you go into the project 'armed' with some knowledge, the outcome is likely to be a whole lot better. And you may not have to chase your tail around in circles on a project.

Carbs can be a bit confusing, but there is a reason why all those extra thingies are hanging off it. You just have to find out which ones go where.

The reason I'm advising getting some theory behind you is from an experience of mine: After a rebuilt engine installation on my truck, the thing would immediately go to Wide Open Throttle whenever we tried to start it. Drove us nuts for a week, until I got a fresh vacuum diagram from the Library. It turned out that we hooked a vacuum hose up wrong, and tied the Manifold vacuum port directly to the Cruise control actuator. Vacuum pressure pulled the throttle WFO. A couple hoses rerouted correctly, and things all of a sudden started working right.

Good luck, and happy hunting,

Remember: It's not just a car. It's an Adventure.
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post #3 of 3 (permalink) Old 07-14-2011, 01:34 PM Thread Starter
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Scott, I have been sitting back for some time thinking about this. I have to find a way around the emissions switches. I am considering blocking off the retard end of the distributor advance and connecting the advance side to the manifold. From what I have read, I really don’t need the idle shutoff solenoids so the fact that they have been cut off is an indication someone else knew this also. My rebuilt carbs passed the tests at the shop and I have to clean the whole fuel system out and start from scratch with the fuel supply system.
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