My SL has been having an intermittent cold start problem.
It runs like crap; missing, backfiring, etc. on occasional cold starts and sometimes after running for a while. Once it warms up, the car runs like it should.
I've read about a cold start valve and a corresponding system... could this be my problem? Or do you all think that it might be some other issue?
I don't want to buy parts I don't need, but I do drive the car nearly every day and I would like to not wonder if I'm going to stall in the middle of rush hour traffic.
Any suggestions would be greatly appreciated.

 

Why dont you try cleaning the air intake system using the carburetor cleaner or carbon cleaner spray? Have you done on this on your 73 450SL?

possiblity of cloggs by the dirty / carbon deposits internal parts from the air inlet can make the cold start a choking start. Once your car is warm up it goes fine. Well I suggest you do the spray 1st... you dont have to dismantel much but just spraying it into the throttel fly and let it dissolve and burn off it to smoke exhaust. FIY read the spray instructions before using it.

Update us on your findings


Rockerfella174

Brunei Darussalam

 

I tried using some throttle body cleaner. It seemed to help for a while, but it may have just been the car playing tricks on me. Today, in traffic, it totally died. I walked home, got another car and went to where the benz sat. It started immediately and I was able to drive it home with no problem.
So, I'm extremely confused...
Could it be fuel pump? The only thing that makes me think this is not the problem is that the car sometimes will backfire. I always thought that was a symptom of flooding, unburned fuel com-busting outside of the combustion chamber. But, there is a noise that has recently developed that makes me think the pump could be part of, hopefully all of, the problem.
Any other suggestions? I'm totally at a loss here.
Thank you

 

Do you know any reputable "A" mechanics? Because it's a 74, it will take a lot of hit and miss to get close to the actual problem. I would start off with an old fashioned tune-up, and take it from there. Good luck.

 

I had a similar issue with my 74 450 SL. Turned out to be an issue with the points. simple/cheap fix and the car ran like a champ. The Cold Start valve/sensor is very expensive. Points are cheap. Give it a try.

 

I meant to tell you all this earlier:
The reason why I didn't consider the points to be the cause is that I just replaced them, no more than 2,500 miles ago, along the spark plugs and distributor cap/rotor. But, I called a mercedes tech and he suggested trying to replace the points, and said that a set can go bad in that amount of time if they were bad to begin with. With new points, the car now runs just like it always did. Problem solved, until the next one develops....