380SE - High fuel consumption : Diagnosing the Cold Start Valve

[amit]

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.

[Benzmac]

Be sure to have someone check the fuel accumulator. It is in the rear of the car at the fuel pump area.

[amit]

Donnie,

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 ?

Thanks,

Amit

[stevebfl]

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.