serejuan

2006 R350, puzzling cranking issue:
on the average, about every 5th time I go to start it the starter cranks for about 1 second and stops cranking right before starting the engine. Here are some facts:


The battery is fully charged and strong, fairly new, even with a booster battery connected it does it.
I've replaced the CPS (crank position sensor): did not help
I've swapped the starter relay with a similar next to it: did not help.
to test it, I left the headights on with the engine off for a long time to drain the battery and see if it's that but it's the same behavior which tells me that it's not battery related.
The RPM needle does not more or jump up as some have stated which would point to signaling the starter that the engine has already started, I understand this is sometimes solved by greasing the starter/flywheel but doesn't seem to be my problem.


When it starts, it runs perfectly and does not cut out.

what could it be? Starter? maybe replacement CPS is also bad? anything else to try?
What actually tells the starter to stop working? everytime that it stops it's exactly the same time, about 1 second, and the engine needs about a quarter second more to start....
Thanks!
Sergio

serejuan

The starter cranks the engine and it seems that right on the first combustion everything shuts down, engine, starter and accessories (windows don't operate,etc). the battery is good, did a load test, cps is new, I've lube the ring gear and starter, but its coming down to the key or EIS I believe. any ideas? this happens on the average every 5 starts but very inconsistently. at times I do notice that I have to apply a bit of pressure so the key to have it click/recognized.
Thanks

Bavarianguru

I am having the same issue on my R500, which gets me to think it's some type of electronic issue. Maybe software issue and such. Or maybe the key fob. In my case, it's occasional and at first it wants to turn over but cuts of, then a few times try won't even turn it. I got power as well. I just realized and figured out that if you hold the key on start a few seconds, it does start. Try that and see if that's the same case for you. Hope that helps and hope we come to a conclusion before taking the car to the dealer. Oh by the way, I have replaced the fuse/relax box in the engine compartment thinking that it was a relay contact issue because the guy I bought to car from would wiggle the starter relay and it would start. But now that it's still doing it, that's completely BS!

serejuan

I was told that the key fobs do go bad and they cause all kinds of strange behavior, so I got a new key and since 1 week now I haven't had any non-starts, i'm very happy (knock on wood...). To get a key there is only one way: go to the Mercedes dealer with the car and a title or registration under your name, and your drivers license. I will take 2-3 days. A nice byproduct is that I have a brand new shiny key fob, while the other one was quite worn out.
If this doesn't happen to be it, the next thing is the EIS, which is what the key goes into, they apparently also go bad.
I hole this helps.