W123 with M110 cold start issue
 

Hi guys, my 280E has a cold start issue whereby it fires but dies a couple of times before finally catching and slowly building up a decent idle.

A mechanic friend has identified a split diaphragm in the part circled in red below, a kind of vacuum valve.

Can anyone tell me the actual name of this part, or a part number, so I can search for a known good one? Thanks.

https://uploads.tapatalk-cdn.com/202...36c1f4d836.jpg


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It is a "Decel Circulating Air Valve"

Hey thanks so much. This enabled me to find the part.


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If replacing that part is not the fix, and it will help but it might not fix it entirely, then move on to the next step.

Try shooting some starter spray into your intake and see if it fires right away. It will then need to idle until it reaches operating temps.

If this works then check out the operation of your warm up regulator. I have had them go bad and this cold start situation is what happens.

Also, if it is your warm up regulator, then you engine will start nicely and run smoothly when it is warm. Just another simple test.

Thanks a lot. We have the warm-up regulator out and ready to send to be tested by someone who has the right bench and testing gear.

One question: aside from the warm-up regulator, does the decel circulating air valve have any role to play in cold start-up issues or is it more likely issues with the auxiliary air valve?

Thanks. I will post updates when we have some success.


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You can test the warm up regulator by sucking on the vacuum port. If it holds vacuum you are good on that part.

The electrical plug has two poles. Depending on the unit you check for the ohms across the poles. The acceptable range is 20 to 40 ohms. Anything above or below that and the unit is bad.

If the vac holds and the ohms are right then that's all there is to test. If they are not then I am clueless as to how to proceed except to find another one that works or get your rebuilt.