OM642 cold start issue (Glow plugs and relay changed!)

[moodi]

Not long had our OM642 but, as title, have an issue where the car takes a while (between 5-7 cranks) to start after being left overnight.

We have changed all glow plugs and also the glow plug relay (for the revised version). All Beru. No improvement unfortunately.

Will try again tomorrow and keep a closer eye on the glow plug light.

I have an Icarsoft so can check things if anyone recommends something like fuel pressures etc. Happy to hear what we should try next!

 

[mersum1es]

try turn key back and for beween zero and ingintion position (let it be few seconds there each time) couple of time, does it improve starting?

 

[moodi]

Leaving the key in ignition position for a few seconds longer before starting initially (first cold start) cures it completely.

Also, like I said, after first time starting it is fine unless then left for several (i.e. overnight) hours

 

[mersum1es]

So you have a small leak somewhere in low pressure system and/or lazy delivery pump

 

[Allybassman]

My OM642 is the same, I turn the key to the on position, allow the glow plug light to go out and crank it after that. If I just turn the key straight to start it can take a good 5-7 cranks.

I think my 'issue' - not sure it is one or not! Is the fuel delivery pump as if I leave the key in the on position for 30 seconds or more and then crank it, it can take 5-7 to start like it would if I just hoped in and turned to key to start straight away. Almost like the fuel is priming, then the pressure is going back down again? I hope that makes sense.

I don't know.... either way I don't see it as an issue.

 

[Lafetoo]

Clean battery terminals, electricity conductivity plays important role during ignition.

 

[OneForTheRoad]

mine was the same after replacing everything, i ended up just giving it 2 or 3 heats and was better.

 

[moodi]

mine was the same after replacing everything, i ended up just giving it 2 or 3 heats and was better.

I think you are right. My issue has gone away, so it must have been related to either the glow plugs or the relay. Strange it needed a couple of cycles of heat to settle down. Seems to be good now.

 

[Chazz9001]

I bought my 2010 CLS 350 early this year and also have the same problem. What I do know is that the glow plugs are there to pre-heat the fuel prior to each ignition to aid cold starting ( which is more of a necessity in winter). There were times when I would have to heat cycle 5 to 8 times before cranking but now summer is here it will start with 1or 2. This suggests to me that my problem is definitely glow plug/relay related and not fuel pressure related. After doing some research I have found there are three types of glow plug for this engine. The 4.5V, 7V and ceramic. What I need to know is how can I tell which plug I need ?

 

[OneForTheRoad]

I bought my 2010 CLS 350 early this year and also have the same problem. What I do know is that the glow plugs are there to pre-heat the fuel prior to each ignition to aid cold starting ( which is more of a necessity in winter). There were times when I would have to heat cycle 5 to 8 times before cranking but now summer is here it will start with 1or 2. This suggests to me that my problem is definitely glow plug/relay related and not fuel pressure related. After doing some research I have found there are three types of glow plug for this engine. The 4.5V, 7V and ceramic. What I need to know is how can I tell which plug I need ?

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