My 2010 E550 4matic was getting hard to start for some time. The first rotation or two of the starter would sound like it was bogged down, and then it would kick in and try to start for 4-6 seconds before finally starting the engine. Finally about 2 weeks ago it wouldn't start at all, and the battery died from the attempt. I replaced the battery and the car seemed to start without any issues. I read a few things online about this happening, so I bought a replacement starter, but wasn't quick enough in getting it installed and now when I turn the key to start the engine there's not a sound from the starter (no click, no anything). A couple of taps on it didn't do anything either. All of the other systems work though as if the car started (lights, gauges, Command, A/C, etc.). I will get the car towed to get the new starter installed, but I decided I'd check the fuses first to make sure none of them are bad. They all seem good (I didn't test the starter relay yet), but as I was under the hood I noticed a mouse nest near the fuse box.

The nest surprised me, as I park the car in a garage and I can't quite make out what the nest is made out of. While I don't see any wires chewed all the way through, one in particular that appears to lead to the wheel well is showing a bit of copper. Can anyone identify what this connector leads to? The first picture is to orient you (the driver's side of the car), the other 2 show the harness. Everything seems to check out when I connected it to the STAR/Xentry software I have except for the left and right Airmatic, which I would imagine is because the engine isn't running (I'm not an expert on using it, I just ran the quick diagnostic). Any other tests I can do to verify the starter is shot?



Close up


Location of the harness (down this area)


Close up

 

I can't make anything from the pictures, but then I don't know the engine.
Just to point that those cars have starters activated by computer, who is checking the voltage before doing so.
Meaning observe the car voltage (on cluster) when you turn the key to eliminate possibility that the starter might be good - just computer is seeing too low voltage.
In over 20 years of maintaining MB for whole family I replaced starter only once - SL500 with 192 k miles.

 

Thanks, the relay tests good (and I can hear it clicking when I try to start the engine), and the battery is good.

 

The relay in the fuse box? Next step in testing would be finding the starter activation wire and jump it, or check for continuity.
Starter winding very seldom fails that is why I would test other possibility before diving under for starter pull.
In the only case I had it was overrunning clutch that failed.

 

the starters on these cars are notoriously crappy. I'm on my 3rd starter within only 75K miles, original starter went at 55K.

Also, Bosch sells a few different starters with the EXACT same part number. The first replacement starter I bought was smaller than stock, installed it and it lasted about 18k miles and then it suddenly died. Actually before it died it started cranking slower and dimming the interior lights, like a bad ground.

The 2nd started I bought, same part number as before, was substantially larger in size. Installed it 2 months ago, seems to be holding up still, also it starts the car much faster than the previous smaller starter.

Here is the 1st replacement starter that died after 18K miles on the left, and the 2nd replacement starter that is on the car now on the right. Look at the size difference, and see how they both have the same part number.

 

I love that they say "Do not strike with hammer"!! I'm curious if they changed anything between the two parts.

 

Are those new, or rebuild starters?
Slowly turning starter indicate couple of armature coils burn out.
When some parts on newer MB have shorter life span, than on older models, I read MB article that my W212 with ECO restart has starter design to handle 8 times more restarts than previous model. My E250 with 183k miles has starter turning perfectly so far.
DPF is another story, that I posted in diesel section.