1999 C250 Turbo Diesel starting problems (W202)

[Henn Hatt]

1999 model, only 52,000 miles, full service record.....
Difficult starting after parked for about hour with heavy diesel fumes under engine hood, caused by worn seals on fuel line system at inlet to diesel filter. After replaced original rubber seals from MB dealer - problem solved - started by the flick of the key, idle smooth like sleeping baby BUT touch the accelerator pedal, EDC warning light comes on - NO accelerator functioning.
This happened miles away from any dealer in the country side of South Africa, to expensive to load and transport to any MB dealer. Swap accelerator control unit (rheostat) with another car - no difference. I urgently need technical data, advise with schematic diagrams and values because Mercedes South Africa do not assit with any.... The person working on the car is a retired Electro Technical Engineer. Your help Much appreciated

 

[Iain]

I would start with getting the fault codes read thru the diagnostic port by an auto electrician. This may well point you to the problem immediately.

 

[GazCaff]

According to the Haynes manual, replacing the throttle pot means it needs recallibrating at an MB dealer, so diagnosis by elimination/substitution may not have isolated your problem in this case.

The only other idea that comes to mind is that there is a problem with the mechanical throttle actuator on the fuel pump, although I have no idea where this is located on the fuel pump and if indeed it is a DIY repair. I seem to recall that the VAG TDi engines which also use a drive by wire throttle have a servo operating a cable to control the fuel delivery on the fuel pump. I daresay the 250 has a similar set-up. Sorry I cannot be more helpful or more specific.

 

[Dieselman]

The fuel pump actuator is a variable magnetic solenoid fired directly from the ECU.
The problem sounds like there may be no speed input so the ECU won't allow the engine to rev past idle for safety.
The engine speed is taken from the crank sensor or substituted by the alternator if necessary, the fuel pump speed is taken from a sensor in the fuel pump.
You really need the codes read before any diagnosis can be made.