QuestionQUESTION: Hi..Just bought 380 and car started running rough till stall. Replaced wires and plugs, it ran like a dream for 100 mile then started rough till stall..Im sure its vacuum, but cant find where vacuum may be failing...any ideas??? Thanx Mike
ANSWER: what year? Kjet or DJet system? how many miles
Starts good cold?
Stalls when hot?
Starts hard when hot?
More information you give me the better!
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QUESTION: Hi Ron...Thank you for your prompt response. 85 380SL 139k Not sure of Jet system or how to differentiate.. Yes it starts well when cold, stalls when hot, yes starts hard when hot, and it just feels like its dyeing .. On the open road she runs well, I just noticed today on the open road as the temp got closer to I00 I could feel it getting a little rough even though I was at 75mph. Now that you mention it, it does start loose life when driving in traffic etc......What I do notice is like a buzzing sound at the back, that I presume is the fuel pump..I only notice the noise when the car is running rough...
ANSWER: Ok then it is a Kjet system The buzz is the fuel pump and it may be normal or it may not be, they should buzz but a loud buzz and vibration may not be good,
Hard hot start problems are a little more dificult to anaylze -
Are you handy with tool and tesitng equipment ?
common causes are defective fuel pump check valve, leaking cold start injector, or low fuel pressure, airflow sensor plate hieght, binding control plunger, or leaking injectors
was this a sudden onset, is the fuel pump noise new?
If cold starts are good , I would look to fuel delivery , leaking injectors or low pressure at the fuel rails, bad fuel pump
The K jet requires a systematic approach to diagnose. I would make sure fuel delivery is good
and then look to injectors
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QUESTION: 380 SL - Just to say that hot start is not really an issue, only after the car fails is tough to start. Just give it a 5 min rest and it will start but run very very rough until it stalls. Thank you for your time....
Answerpull a plug and tell me the color of the tip. I would venture to guess your cold start vavle is faulty or you injectors are faulty.
Have the injectors been cleaned or checked, are they original?
Both ( injectors /CSV) would cause an overfuel condition and make it run badly
