C250d - First start troubles

[MrABC]

Hi all,

New member here hoping for some guidance on an issue.

I have a C250d (W205) which cranks for 10 seconds before the engine starts but only when I start the car for the first time. After this it is absolutely fine….no struggle to start at all through the day. There is no performance drop and it drives absolutely fine.

There is no engine management light showing and I recently had the battery, fuel filter and glow plugs replaced at my local dealership. Still no resolve. Mercedes then suggested I replace the engine as they can’t find the fault (they had the car for over a week and had a Master Technician look at it they say). The car is almost 10 years old so I’m definitely not doing this. They thought it might be the fuel rail so I agreed to have it changed at over a grand BUT during testing they found it hadn’t resolved the issue so fitted my original one back in at no charge.

I have maintained the car to schedule at either the dealership or a reputable Indy in Bham.

Any suggestions on what this could be? I fear having to move it on next month as I don’t want it to breakdown on me.

Many thanks in advance!

 

[DSM10000]

I think the best advice is to not use Mercedes but find a well respected Independent specialist to investigate the problem.

 

[MrABC]

I think the best advice is to not use Mercedes but find a well respected Independent specialist to investigate the problem.

Thank you for responding.

I did speak to my local Indy who said this could be expensive because they will have try things out in the hope of finding the problem. Parts won’t be cheap and it will be trial and error. Had the engine management light been on it would be easier.

I get the feeling this issue has most mechanics i have approached stumped

 

[alecmascot]

The next time you start the engine from cold open the bonnet, remove the engine cover and listen in the region of the fuel filter to hear if it is filling when the key is first turned. If you can hear fuel flowing at that time then you have an air leak in the fuel system and the fuel is draining back into the tank overnight and the filter is being filled the first time you turn the key from cold. Have a listen and see what it sounds like.

 

[MrABC]

The next time you start the engine from cold open the bonnet, remove the engine cover and listen in the region of the fuel filter to hear if it is filling when the key is first turned. If you can hear fuel flowing at that time then you have an air leak in the fuel system and the fuel is draining back into the tank overnight and the filter is being filled the first time you turn the key from cold. Have a listen and see what it sounds like.

Thanks for the suggestion. I’ll give this a go and feedback for sure

 

[Smiley]

This is a symptom of the glow plug relay....was that changed at the same time as the glow plugs?
It would have been number 1 suspect ime
And it is cheap and easy.

 

[MrABC]

This is a symptom of the glow plug relay....was that changed at the same time as the glow plugs?
It would have been number 1 suspect ime
And it is cheap and easy.

Thanks for the reply! No, they changed the glow plugs and tested the pre glow system - according to the invoice.

Your suggestion is on point as I’m reading the same suggestion mentioned during my research. I will get mine replaced and see how it goes because as you say, it’s a cheap repair.

 

[Supernoodle]

Thank you for responding.

I did speak to my local Indy who said this could be expensive because they will have try things out in the hope of finding the problem. Parts won’t be cheap and it will be trial and error. Had the engine management light been on it would be easier.

I get the feeling this issue has most mechanics i have approached stumped

I'd suggest taking to someone who knows how to diagnose and test. Even if there was a code, it just tells you what to test, you don't just go replacing parts.

To decent mech should be able to ascertain if there is fuel in rail, it's at the correct pressure and whether it's being injected. That would tell you a lot.

 

[MrABC]

I'd suggest taking to someone who knows how to diagnose and test. Even if there was a code, it just tells you what to test, you don't just go replacing parts.

To decent mech should be able to ascertain if there is fuel in rail, it's at the correct pressure and whether it's being injected. That would tell you a lot.

Fair shout - I’m scheduled to visit my local specialist next week so