Surging Engine After Cold Start

Robski

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Joined
Apr 1, 2016
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Location
Wellington, New Zealand
Your Mercedes
Looking to buy a R107
Hi, my 1971 350SL (with Bosch D-Jetronic fuel injection) starts and runs no problem, but when the start is from cold it will run well for around 30 seconds, but then start to surge between 1000rpm and 2000rpm for around a minute before settling down to what I guess is a normal high (cold) idle speed that decreases down to 750rpm once its fully warmed up.

Does anyone know (or can help me diagnose) what may be the problem here?

Robski
 

ajlsl600

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Joined
Nov 18, 2013
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5,494
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Location
france
Your Mercedes
clk3202001,sl6002003 with everything regrettably sold ,A class 170cdi auto. NG/TF1800 ML250
has that car a seperate injector in the manifold somewhere thats playing up.or its drawing air from somewhere for a while.. would say a fuel air issue . i remember some fuel injector ,petrol systems used to have another injector in the manifold for the coldstart
 

ajlsl600

Senior Member
Joined
Nov 18, 2013
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5,494
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2,707
Location
france
Your Mercedes
clk3202001,sl6002003 with everything regrettably sold ,A class 170cdi auto. NG/TF1800 ML250
so it does have a cold start injector. now on some systems like bloxxy lr the cold start injector was 6v whilst engine running injectors were 12v . tell me that was,nt just so you never had a spare !! if thats not the case here, maybe you can swap them? or just pull the plug and see the difference.OP says it does settle down , struggling to see where air leak that heals itself regularly and after a few moments would be. and if so it would likely be electricaly controlled . too quick to settle for it to be thermostat controlled.
 


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