Daniel Crilly

So I know there are a million possible reasons for this but perhaps with a little background someone might have an idea where to start.
I'm going to take it to my local Mercedes mechanic (not a dealership) but I've only just found him so I'd like some ideas before I take it to him.

2007 E280 with 304,000 km
Just bought it in October.
Been a daily driver since with no issues.
Had the speed detector rings (ABS etc) replaced in December. (at the same place I am going to take it to)
He told me I would need a new thermostat but that it was not crucial but expensive so I decided to wait.
Cabin does not heat as fast as it should in the winter but it is nothing uncomfortable so I have been fine.

Suddenly the other day it would not start.
I had driven it just the previous evening home from work with no issue.

It turns over but the motor will not start.

we have had a couple of cycles of freezing, above freezing and then below freezing again. The above freezing periods were very wet with lots of water on roads.

It had turned cold again overnight the night before it would not start and it has remained cold since so I have not had the chance to see if it might start in "warmer" (+5C) temps.

No idea if any of this is relevent but just in case there it is.

I'd love to know if anyone has any ideas...

Thanks

Dan

05w211wagon

Daniel, I would look at the crankshaft position sensor (CKP), if its not the batteries.

Thanks

tjts1

+1
Swap the crank sensor. I keep one in my stash of spare parts when I'm on the road. It's the most likely component to leave you stranded.

Daniel Crilly

Thanks for responding!

It started with no issue the day after I posted this but now again it is just turning over.
If it was the battery surely it would not turn over, am I wrong?

EuroDriverSD

You are correct - if the battery was dead, it would not turn over. As others suggested, the crankshaft position sensor is the most likely culprit. However, if that does not fix it, you are better off having a diagnostic done because like you said, it could be one of a myriad of things. In my case when this happened to me it turned out to be a very rare failure - the throttle body.

05w211wagon

update?

kajtek1

I am not familiar with the engine, but in each situation of non-starting the easiest way to start troubleshooting is read the fuel pressure.
Some cars will show it on scanner, for older you need $19 gauge.
Bad CPS usually start acting on hot engine, while still working on cold one.
I never could get solid confirmation, but working CPS in no start situation should move tachometer a little?