E350 - slow starting

[jinsole]

Hi everyone,
My E350 bluetec (OM642) always seems to take a little longer to start when I’ve left the car for longer than a few hours. Doesn’t seem to matter what temperature it is because it still does it when it’s 25 degrees. Once i’ve started it for the day, any subsequent starts fire up quickly. It always starts but the first time in the day it can take up to 3-5 seconds. The glow plug light only flashes during starting for less than a second even when it’s slow to start, and there are no error codes.
I’ve read a few posts mentioning could be the control module, which I’d happily replace as it seems easy to do, but I’m just wondering if anyone else has has similar symptoms before I start the trial and error process.
Failing that, I’ll probably just take it to the indie to diagnose and sort.
Cheers

 

[TeddyRuxpin]

98% chance it's the glow plug relay. It's a pretty easy DIY and a low cost fix

Yes, I had the same symptoms. They get gradually worse and worse.

 

[jinsole]

98% chance it's the glow plug relay. It's a pretty easy DIY and a low cost fix

Yes, I had the same symptoms. They get gradually worse and worse.

Easy DIY and low cost always sounds promising When you say low cost, is that using a non Merc branded part such as Meyle or Beru? I’m not sure which one I would need. I don’t mind buying OE but not if it’s just a premium for having a Merc logo on the same part.

 

[TeddyRuxpin]

It's literally just a Merc logo and MB tax added - get the BERU!

 

[jinsole]

Brilliant. Thanks!
Do you happen to know which one or how I can check?
My engine code is OM642.838.

 

[jinsole]

I thought it might be the GE115 but not sure.

 

[BTB 500]

As an aside OM642 relay units were in short supply for some time ... MB certainly didn't have any last year. There's also a 225A 'mega fuse' for the glowplug circuit, which had blown on mine.

 

[jinsole]

cheers for the heads up. All the more reason to try and source one myself.
That’s one big fuse!

 

[jinsole]

I’ve just checked the part number of my existing glow plug relay. It is a6429007901
I was going to get the Beru GSE116 replacement. It looks the same but websites say it is incompatible. I don’t suppose anyone knows which is the the equivalent is?

 

[TeddyRuxpin]

That's the one I used, however I'm only familiar with the 'blue efficiency' engines, the 231bhp and 265bhp ones without AdBlue. Is yours a later engine with adblue?

I'd guess it's the same but it's definitely worth checking if you don't have the earlier W212 engines

 

[jinsole]

Hi Teddy. Yes mine is the ‘bluetec’ engine with adblue.

 

[jinsole]

Update for anyone in a similar position. I decided to get a used but newer merc replacement on eBay for £35 (they said it was fully working). I didn’t want to spend much more in case it wasn’t this part that was faulty. Luckily the car now starts with no issues at all. Thanks for everyone’s help.