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Old 01-23-2003, 07:58 PM
Registered User
Join Date: Dec 2002
Posts: 75
380SE - High fuel consumption : Diagnosing the Cold Start Valve

From previous posts, I gather that the high fuel consumption could be because of (1) a faulty cold start valve or (2) a faulty warm-up regulator.

Question is - how do you troubleshoot / diagnoise a faulty cold start valve ? How do you diagnoise a warm up regulator.

Here are some symptoms:

1) Starts great when cold
2) Takes a few additional turns of the engine to start when warm
3) Starts with a stumble when warm and you just let go of the key after the first turn.
4) Slightly rough idle when warm. Smooth idle when cold.

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Old 01-23-2003, 08:12 PM
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Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
Be sure to have someone check the fuel accumulator. It is in the rear of the car at the fuel pump area.
Donnie Drummonds
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Old 01-24-2003, 01:35 PM
Registered User
Join Date: Dec 2002
Posts: 75
380SE - High Fuel Consumption


The MB dealership replaced the Fuel Pump and Filter only 2 months back. Wouldn't they have pointed out a faulty fuel accumulator.

Also, from your experience, can a faulty fuel accumulator cause excessive fuel consumption ? I can check it. What should I look for ? Leaks ?

Which would be the most likely culprit ? Cold Start Valve ?


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Old 01-24-2003, 06:29 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
A faulty accumulator could account for all your symptoms except fuel consumption.

The only way the cold start would affect fuel consumption was if it leaked. If we were talking a US 380 then proper fuel consumption will likely occur with proper timing and closed loop fuel control. Read the archives about monitoring the duty cycle of the frequency valve at pin #3 of the diagnostic socket.

Proper monitoring of the duty-cycle can allow the proper mixture adjustment without exhaust gas readings.

Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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