C220D EDC warning light etc

chriss

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Jan 10, 2004
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Just purchased a high miles 1995 C220 Diesel and, amongst other things, I have what seems like an expensive (i.e. non DIY) problem: the EDC warning light comes on (intermittently) and also the engine revs are sometimes limited to about 3500 RPM. There is no simple correlation as sometimes the revs aren't restricted, at least in neutral, although they are most of the time under load, and the appearance of the EDC light and the engine performance problem are not firmly linked i.e. if the light is off the revs can still be limited. When switching off the engine runs for about 3 seconds before stopping, and cold starting is poor.

I presume that this is a problem that can only be bottomed by specialist diagnostics but if any one has had similar problems I would be interested to hear from you.

Thanks
Chris
 

Dieselman

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As you have already worked out the EDC light is indicating a problem with the diesel control. The light will light only if the problem is deemed serious enough, otherwise the ECU will adopt "limp home mode" and reduce power.
Power reduction is performed by reducing fuelling.

This is probably nothing major and could be due to poor connections or wiring fault, a faulty sensor such as accelerator position potentiometer.

If you are fairly competant with a meter start checking around, if not take the car to a Bosch diesel centre for diagnosis.

People get worried about EDC, don't be, there is very little electronics in the pump, only a solenoid to pull the rack to increase fuelling.

This system is a mechanical system with electronic control so diagnosis shouldn't be too difficult.

The stored fault codes should reveal all.
 
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chriss

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Dieselman- thanks for your reply, I'll have a poke around and see what happens.
 

riz

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Dec 11, 2005
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Hi,

I have the exact same problem with my '95 C220D 90k which i have just bought. I don't think the EDC light is working in mine as it doesn't light up when i turn the car on.

The car does not rev over 3500 even in neutral and i assume its in the limp home mode. The air flow sensor does have tape around it which makes me a bit suspicious.

Anyway, I had a similar problem wih my Vectra and it turned out it was the Air Flow Mass sensor. The only difference with this is that when the engine is switched off on the merc it stays running for a few seconds and this did not happen on the vectra.

The way i checked this problem on the vectra was disconnecting the sensor. By doing this the ECU light would stay on constantly but power would be restored. I wonder if this would work on the Merc?

The other thing it may be is the fuel pump as i have been reading on this forum quite a few of the members had this problem

Please help, this is my first Merc and i don't want to be put off by them.

Cheers
 

Dieselman

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riz said:
Hi,

I have the exact same problem with my '95 C220D 90k which i have just bought. I don't think the EDC light is working in mine as it doesn't light up when i turn the car on.

The car does not rev over 3500 even in neutral and i assume its in the limp home mode. The air flow sensor does have tape around it which makes me a bit suspicious.

Anyway, I had a similar problem wih my Vectra and it turned out it was the Air Flow Mass sensor. The only difference with this is that when the engine is switched off on the merc it stays running for a few seconds and this did not happen on the vectra.

The way i checked this problem on the vectra was disconnecting the sensor. By doing this the ECU light would stay on constantly but power would be restored. I wonder if this would work on the Merc?

The other thing it may be is the fuel pump as i have been reading on this forum quite a few of the members had this problem

Please help, this is my first Merc and i don't want to be put off by them.

Cheers

Try disconnecting the MAF and see if it alters the problem.

the EDC light will only illuminate if the problem is serioius enough and won't light at switch on.

You mention the engine runs on at switch off. I think this may be the stop solenoid may be stuck, possibly part open, so fails to switch off but also may fail to deliver enough fuel under load also.

The fuel pump has a solenoid motor, and two positioning sensor coils, no fancy electronics. Diagnosos shouldn't be too difficult but may need the codes reading.
 

riz

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Dec 11, 2005
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Disonnected the MAF, no joy.

I've realised that as soon as the car is started, for about 10 seconds, the revs aren't restricted. But after 10 seconds they are.

There is also a strange buzzing/ticking sound coming from the glove box while the engine is running???

Starting the car is also takes a bit of encouragement after it has been parked overnight.

Will get the codes read this week, will have to see what happens.

Where about is the stop solenoid and the fuel pump?
 

TOI 287

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Jan 25, 2006
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E240 Avantgarde Estate
C220d

Hi

I have been following this conversation. My C220d has developed precisely the same problem. My local garage has told me that they don't think that it is the pump but more likely to be a relay not connecting properly. Plausible?
 

Dieselman

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Possible.

If teh stop solenoid or fuel pump relays are not supplying enough juice then you will have a fuel starvation problem.
 

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