Thread: Rough start
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Old 04-12-2002, 10:56 PM
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Re: Rough start

Originally posted by John Coleman
My 95 S420 starts fine cold and immediately after engine is turned off. However, if I start it 30minutes to an hour after running it, the engine is very rough for about 30 seconds. I have replaced distributor caps and rotors and checked plugs. I have also replaced the fuel filter. Any ideas would be welcome.
Sounds a lot like my 450SEL. I hazard a guess that the fuel accumulator may be bleeding off pressure.
Put on your diagnostic cap:
It wouldn't be anything in the ignition system if the problem is transient.
It would not relate to the filter if it is merely a starting problem.
Sounds like a temperature/time problem:
OK. What happens to a warm engine that does not happen to a cold engine?
Fuel vaporizes. So?
It empties out the fuel rail giving you a hard start where vapor has to "bleed out" before nice liquid is available for your engine.
Accumulator maintains pressure in your fuel lines.
What else?
Maybe you have a leaky injector that dribbles a pile of gas while sitting, causing that cylinder to not fire until the engine has cleared that one cylinder out.
I will post the cure to my car's *****y hot-starting. . . . .
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