I have a 99 C230K with 55,000 miles. Recently it developed a hard to start cold start.....shakes and stalls at the first start attempt and then catches but hesitates for about 5-10secs at the 2nd attempt. Then its all good for the rest of the day until it sits for 8hrs or so and you turn it on again, such as the morning.

I was told the fuel pump makes the pressure and it likely the cause. I was thinking based on older MBs and how they run, that it would be some type of cold start valve or the like.

Anybody have an opinion? Please help!

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99 C43
98 S420
99 C230K
01 C240

Test the coolant temp sensor first

How do I go about testing it?

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99 C43
98 S420
99 C230K
01 C240

Anyone else have an idea?

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99 C43
98 S420
99 C230K
01 C240

you probably could do it with an ohm meter...
and you gone have to find some way of heating it up you could probably do it in car, hook your ohm reader up start enging and watch

it's just a guess, but thats what i would do