W163 ML270 CDI Glow Plugs issue

ldare

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Hi,

Both this and last winter I've had real trouble with the glow plugs on my 2003 ML270. The glow plugs have been changed, and so has the rely. In the summer the car starts perfectly, in the cold it really needs to turn over to generate enough heat and if below zero will not start at all.

Previously people have mentioned it could be fuel starvation but I believe that's not the issue.

What's the best way to both test if the glow plugs are getting power and also are there common places that fail that could be preventing them from heating up?

I've taken it to a few garages, some have said live with it, some have said they can't find a fault. The issue now is when it dropped below zero last month it wouldn't start. It started fine the next day after I opened the hood and let the sun warm it up a while first.



Thanks
Louis
 

Wighty

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When you say garages have looked at the car , do you mean a good Mercedes Independent with the MB Star computer ?
 

mersum1es

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it is not glow plug fault, that engine will start without them at those temps. Besides if your glow plug light works as usual, there is no fault in plugs.

It is 95% either leaky injectors or leak in low pressure pipelines (draws air in and air bubbles shown in clear pipes). Search O-rings and you will get plenty info... last 5% cover leaky hp-pump, pressure regulator or other fuel line problem/leak
 
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ldare

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When you say garages have looked at the car , do you mean a good Mercedes Independent with the MB Star computer ?
Yes, they said live with it, they said the cost to find the fault wasn't worth it
 
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ldare

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it is not glow plug fault, that engine will start without them at those temps. Besides if your glow plug light works as usual, there is no fault in plugs.

It is 95% either leaky injectors or leak in low pressure pipelines (draws air in and air bubbles shown in clear pipes). Search O-rings and you will get plenty info... last 5% cover leaky hp-pump, pressure regulator or other fuel line problem/leak

We have changed the hp pump and also one fuel line with no improvement. If it was an air lock would this be affected by temp? As I say if it's over 10'c you'll not notice an issue. Noticeable below 9'c and a real issue when there's been frost or snow.

Ta
Louis
 

mersum1es

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No air locks in these systems. Do you see air in clear lines? If no, measure injector back leak. It is typically very temp sensitive. You may try heat injectors by heat gun or hair dryer, sometimes it helps and fault pinpointed.
 
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ldare

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No air locks in these systems. Do you see air in clear lines? If no, measure injector back leak. It is typically very temp sensitive. You may try heat injectors by heat gun or hair dryer, sometimes it helps and fault pinpointed.

If it's starting fine with the weather at the moment would I still have air bubbles or do I need to wait for a very cold morning to investigate? I may have missed the window now for this year.

Many Thanks
 

Taffy7hfa

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Hi Louis, sorry I cant say for sure why yours is struggling to fire up at the moment but thought you may find the following comment interesting, mine has had the "glow plug light stays on for 60 seconds after start up" fault for the last 3 months, which probably means I have 1 or more faulty glow plugs or possibly even a faulty relay, it's my daily driver and has 130k on the clock, I usually leave for work at around 6.30am, it has started every single morning (even the really cold ones !)within 5 seconds of turning the key, obviously I will be replacing all the glow plugs soon to eliminate the glow plug light fault, but my experience with this particular engine is that if it is otherwise healthy they are really not that reliant on glow plugs to start unless its well below freezing, it actually says as much in the owners manual. If it was mine I would be checking the low pressure fuel lines for air leaks, its a really common problem with these and can be the cause of long cranking times, and is often worse in cold weather.
 

mersum1es

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leaky injector will not give usually air bubbles. Yes best result is got when problem is on but I think you could still find something in normal +5c morning test session. Check for bubbles or/and measure leak.
 
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ldare

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Hi Louis, sorry I cant say for sure why yours is struggling to fire up at the moment but thought you may find the following comment interesting, mine has had the "glow plug light stays on for 60 seconds after start up" fault for the last 3 months, which probably means I have 1 or more faulty glow plugs or possibly even a faulty relay, it's my daily driver and has 130k on the clock, I usually leave for work at around 6.30am, it has started every single morning (even the really cold ones !)within 5 seconds of turning the key, obviously I will be replacing all the glow plugs soon to eliminate the glow plug light fault, but my experience with this particular engine is that if it is otherwise healthy they are really not that reliant on glow plugs to start unless its well below freezing, it actually says as much in the owners manual. If it was mine I would be checking the low pressure fuel lines for air leaks, its a really common problem with these and can be the cause of long cranking times, and is often worse in cold weather.
Hi,
This is very helpful the glow plug light doesn't stay on with me,

Ta
Louis
 
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ldare

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Hi Louis, sorry I cant say for sure why yours is struggling to fire up at the moment but thought you may find the following comment interesting, mine has had the "glow plug light stays on for 60 seconds after start up" fault for the last 3 months, which probably means I have 1 or more faulty glow plugs or possibly even a faulty relay, it's my daily driver and has 130k on the clock, I usually leave for work at around 6.30am, it has started every single morning (even the really cold ones !)within 5 seconds of turning the key, obviously I will be replacing all the glow plugs soon to eliminate the glow plug light fault, but my experience with this particular engine is that if it is otherwise healthy they are really not that reliant on glow plugs to start unless its well below freezing, it actually says as much in the owners manual. If it was mine I would be checking the low pressure fuel lines for air leaks, its a really common problem with these and can be the cause of long cranking times, and is often worse in cold weather.

So far we've replaced the High Pressure Fuel Pump, and I believe the 4 o rings with the pipes that connect and also the pipe which clips onto the fuel filter which if I recall goes to the high pressure pump? We'll look at the low pressure lines next.

Ta
 
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ldare

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it is not glow plug fault, that engine will start without them at those temps. Besides if your glow plug light works as usual, there is no fault in plugs.

It is 95% either leaky injectors or leak in low pressure pipelines (draws air in and air bubbles shown in clear pipes). Search O-rings and you will get plenty info... last 5% cover leaky hp-pump, pressure regulator or other fuel line problem/leak
Hi
Me again lol. The low presure line goes from the low presure pump to the diesel filter and the other to the high presure filter by the looks of it? Ordered O rings, am I looking to replace both on low presure pump, 1 on filter, 1 on the rear of the injector section and should I do both on high presure pump? Ones on up pump don't look a quick job?

Thanks
Louis
 
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ldare

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mersum1es

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you will need totally 6 0-rings 2x 264 (plus foamseals 2x267), 2x198, 215, 98, 252. As far I remember all rings are similar but part dealer surely know... There is only two pipes (left side of hp pump). You don't have shut down valve shown in pic left side of pump so your connectors are similar. Remove serpentine belt to get more space there.
 
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ldare

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I replaced A6120703132 fuel line (which had new orings) a year ago but that made no different during the winter of 2017/18 - I'm going to change A6120703232 (again with new orings included) this summer and see what happens when it's cold again. I'll update when I know if its worked. (I didn't managed to just change the orings as A6120703132 was brittle and so ended up replacing the the whole line I didn't continue and just lived with it )

http://www.benzworld.org/forums/att...line-part-number-needed-2015-03-30_045741.jpg

Louis
 

Oddeman

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Did you check the cylinders compression, because if they does not generate enough pressure it will be hard to start even if the glow plugs works.

Oddemann
 
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ldare

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Did you check the cylinders compression, because if they does not generate enough pressure it will be hard to start even if the glow plugs works.

Oddemann
I didnt but I think an issue there would be noticable 365 days?

So far changed:
HP Pump
HP to LP Fuel Line
LP to Filter Fuel Line
Filter
Fuel line from Filter to back
Copper ring on a suspect injector

Just need to wait for winter to see if its cured.

Ta
 

Oddeman

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When the engine is running it will generate enough pressure to run. But the cold start requires a really good compression. Without a good compression nothing else will help. These are the required things to start an engine:

1 Compression
2 Glow plugs
3 Fuel

Oddemann
 


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