W211 320 CDI Poor Cold Starting

andrew056

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1993 SL320 gone but not forgotten , 2004 240 CLK cabrio, 2006 ML 320cdi gone, GLC AMG 43
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Car is 8 years old with 62k miles.
Sounds likely , the relay is fitted is fitted on the front of the left hand bank looking from the front , the original relay was quite boxy looking , the later one is more wedge shaped , if you still have the original that's probably your culprit though I would have thought you would have the glow plug light coming back on for a short time after it does eventually start.
 

Wighty

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So

Sounds likely , the relay is fitted is fitted on the front of the left hand bank looking from the front , the original relay was quite boxy looking , the later one is more wedge shaped , if you still have the original that's probably your culprit though I would have thought you would have the glow plug light coming back on for a short time after it does eventually start.
I changed my relay a few months ago after starting problems , and on my om642 engine the gp light wasn't coming on as a symptom .
 

KennyN

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and on my om642 engine the gp light wasn't coming on as a symptom .

Neither was mine , even though the GP relay was toast according to the STAR check. My GP light only came on when one or more of the plugs was knackered.

Kenny
 

Wighty

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Neither was mine , even though the GP relay was toast according to the STAR check. My GP light only came on when one or more of the plugs was knackered.

Kenny
Yes same here when I had one duff GP
 

6cyl

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Any one have a photo of where it can be found ? My car is a 2009 CLS 320 CDI, the problem is intermittent at the moment.
Thanks
 

Wighty

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image.jpeg
Any one have a photo of where it can be found ? My car is a 2009 CLS 320 CDI, the problem is intermittent at the moment.
Thanks
Front left of engine as you face the car , remove the plastic engine cover first .
 

KennyN

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Held on by two bolts , the outer one has a retaining nut so be ready to catch it but the inner bolt is screwed into the casting with no retaining nut.

Kenny
 

Mr Filipov

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That does not mean parts don't perish over time. Rubber, plastic and electrical components like relays are as much time dependant as they are useage wise.
 

bigshineybike

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C320CDI W203, E300D estate 1996 multivalve, VW 1.9 auto, Triumph T509, Montesa Cota 348
2006 320 CDI . turn the key and the engine cranks by itself until it starts. I think I could have this relay problem. thanks for the photo. do any of you know what this relay does? could it be that its not intelligent enough to know its broken even though it can otherwise tell that the glow plugs have failed?
being a relay can it be mended with a bit of sandpaper?
 

Wighty

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2006 320 CDI . turn the key and the engine cranks by itself until it starts. I think I could have this relay problem. thanks for the photo. do any of you know what this relay does? could it be that its not intelligent enough to know its broken even though it can otherwise tell that the glow plugs have failed?
being a relay can it be mended with a bit of sandpaper?
In my cars case , the glow plug light remained on for a bit when one of the glow plugs had failed and the relay was ok .
I suffered slow starting , and a replacement gp relay for £130 ish fixed that . In this case I think my battery was new as well . I just judged that the relay is a consumable part I would end up changing anyway and did this rather than go to a garage
 

Wighty

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The relay has been dismantled on YouTube and had new fuse wire soldered in , no it can’t be cleaned with sandpaper
 

Botus

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when working correctly this engine should fire inside half a second in any temperature, no waiting for the plugs just turn the key in one go and should be running by the time you realise you'd cranked it

I think relay is the wrong word, its a control module, with later ones running later hardware and software - on these engines like most modern tractors glow plug run on and off all the time the engine is running (not just there for start up) 60k miles all the plug and the module need replacing
 


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