W221 S350 not starting (doesn’t even try) after service.

[alexanderfoti]

Should I read that as ECUs damaged by water ingress or power related, or it’s not the ECU but water ingress or power issues elsewhere?


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No, that commens was in response to Supernoodle. Most ECU faults are caused by an external factor (EG Water getting into the ECU or a shorted injector that blows up the electronic side of the ECU that switches them. The faults in this thread are unlikely to be water related as the EIS is inside the car etc. I am reluctant to comment on your vehicles issues as its obviously complex and all guesswork without the car.

 

[DSK]

Thanks Alex!

If it gets fixed, I will keep it as it’s an epic bus and you and Star will maintain it going forwards. I’d always wanted to do so before but was pretty much house bound due to circumstances until Nov 2023.

All comments from all contributors are highly welcomed so that I can take them onboard, learn new things and also share with the garage to ensure no stone is left unturned.


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[SL500+S500]

I’ve got the same problem on my 08 S500 5.5

It’s had about £3-4k worth of MB garage work prior to my ownership (I bought it off a dealer I know locally): They went through replacing the EIS, passenger footwell module, crank sensor, starter battery, starter etc. I put a new battery in it, Jerry rigged a parcel shelf solar panel/charge controller as I thought it was a volts escaping issue but it still can leave me stranded on occasion. On the last one I sent off the ECU for a check to a specialist and it came back fine - because I thought it was having hot- ECU start problems.

Despite all of this, it will still randomly fail, or fail initially then pretend crank and not start. Fart around; get out/lock/unlock/in and it goes.

It occurred to me TODAY, that the problem might not be ANY of the systems you’ve considered above; I think it could due to the easy-entry. You’ll know that the car won’t fire off the button if the easy entry is moving the wheel or the seat into position. So it must take a signal when the seat module or steering wheel is in its designated position. My car had a failed drivers seat module with parasitic voltage drain, now I’m assuming that if this wasn’t always sending the correct drivers seat position it acts like an immobiliser. I’ve previously replaced the module, but I’m still getting the starting issue. The wetness issue could play into this too as the module sits right over the carpet - damp car/condensation on/in the module.

As a precaution I turned the easy entry fully off and it’s behaved. I’ve tried it a few times today and it’s started on the button without a hitch. I’m going to cold start it tomorrow to see if it works when the car is fully cold.

 

[DSK]

That’s a lots parts.

You say that yours pretends to crank, so it must at least be cranking to some extent? On ours, there’s no crank, clicking or anything.

I read somewhere someone cured their issue by turning of that driver assist thing with the coffee cup symbol. It didn’t work for me. (Do we love in a age where imbeciles don’t know how how they feel?)


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[SL500+S500]

That’s a lots parts.

You say that yours pretends to crank, so it must at least be cranking to some extent? On ours, there’s no crank, clicking or anything.

I read somewhere someone cured their issue by turning of that driver assist thing with the coffee cup symbol. It didn’t work for me. (Do we love in a age where imbeciles don’t know how how they feel?)


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Yeah, doubly for the dealer because he bought the car for his son, coughed a wedge in repair parts to Neyland Merc, then couldn’t get it reliable only for the son’s wife to reject it based on the starting issue.

I get anything from lights only, ignition relays clicking, grinding ignition noises, partial cranks to flawless Starts.

Imbeciles? Everywhere

Edit: I’ve just been outside, slight delay (half a second) then just started on the button. I’ll leave it now until tomorrow.

 

[DSK]

Yeah, doubly for the dealer because he bought the car for his son, coughed a wedge in repair parts to Neyland Merc, then couldn’t get it reliable only for the son’s wife to reject it based on the starting issue.

I get anything from lights only, ignition relays clicking, grinding ignition noises, partial cranks to flawless Starts.

Imbeciles? Everywhere

I meant with all these electronic bullsh!t driving aids, drive assist, tiredness detection and all the hundreds of gimmicks, are only to impress imbeciles.


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[SL500+S500]

I meant with all these electronic bullsh!t driving aids, drive assist, tiredness detection and all the hundreds of gimmicks, are only to impress imbeciles.


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Indeed; the lane departure on the wife’s Shitroen drives me nuts, when you’re skipping along a fast twisty A-road, it keeps on bleeping at me every time I take a ‘racing line’ through a corner.

 

[SL500+S500]

100% starting record today, hot and cold. No false starts, no relays clicking, no total blank.

First time, every time on the button. (That’s the first time it’s been 100% in all situations in a day.)

It’s an incomplete signal from the seat or steering wheel positioner: I’m 100%. It’s exacerbated by a duff battery for sure (in my case) as the time taken to get to the final position is longer and you run out of goes on the battery more quickly, so it feels like a low vol start sometime. If one of those modules isn’t reporting 100% they are acting as an immobiliser.

Edit: except just now, not firing on the button. Nothing, then heard a light clonk after trying the key a couple of times, then it behaved. Ffs.

 

[DSK]

I don’t mean to offend but, does anyone know for sure if there is a seat/steering position sensor that actually links to the start system procedure?


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[DSK]

100% starting record today, hot and cold. No false starts, no relays clicking, no total blank.

First time, every time on the button. (That’s the first time it’s been 100% in all situations in a day.)

It’s an incomplete signal from the seat or steering wheel positioner: I’m 100%. It’s exacerbated by a duff battery for sure (in my case) as the time taken to get to the final position is longer and you run out of goes on the battery more quickly, so it feels like a low vol start sometime. If one of those modules isn’t reporting 100% they are acting as an immobiliser.

Edit: except just now, not firing on the button. Nothing, then heard a light clonk after trying the key a couple of times, then it behaved. Ffs.

Try a new Varta silver / Bosch S5 and see how you get on.


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[SL500+S500]

Try a new Varta silver / Bosch S5 and see how you get on.


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New 95ah AGM fitted Thur.

 

[DSK]

UPDATE

Garage advised earlier this week the car has been repaired and over several tests, the non start issue has not arisen. They are keeping it until mid-late next week under my instruction to modify the drains and continue testing it.


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[SL500+S500]

Update: couple of failures to start over the end of the week, full ignition lights on, but nothing else. The old battery that I took out was dying (I had it checked), which might have contributed extra issues too.

Went through the electrical system with a multimeter checking the functions at as many places as I could; all sound, relays latching in the front fusebox etc. Easy entry made no difference to the system: all reporting 13+volts. Many many attempted starts later and I had one or two partial turns, but not firing.
I went back to a previous you-tube suggestion; fuel pressure issue. The relay is under the rear armrest cubby; however I found the removal/swapping easier by pulling the rear passenger seat back card off from the boot. Checked/cleaned swapped and reseated the relay. Car starts on first turn, no issues.

Failure of the fuel relay to engage obviously means there‘s no pressure in the fuel rail, no reading from the fuel pressure sensor and therefore no start. Also, when you get a start failure, the system subsequently disengages the starter (which I thought was the easy-entry seat shenanigans) to prevent obvious damage to the starter. So you get effective immobilisation, just because the car either thinks there’s no fuel pressure or that the ignition thinks it has started because it’s done all the right stuff. The push button starter also adds a level of complexity to this because you have to keep your foot on the brake and allow bit of a delay before the system allows another legitimate starting attempt. I’ve gone back to the key and it’s made everything more straightforward to work out when the car was problematic; I’ll go back to the button if it the relay swap sorts it.

I’ve just done a shopping trip and it’s behaved. I’ll see if it continues to do so over the next few days.

 

[DSK]

Thanks, this fuel pump relay is also on the just do it list and they will do it next week. They called to say I asked for the sunroof drains to be checked, they can’t as the sunroof doesn’t work… I replied well, it has always worked beautifully and was working so sort it.


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[alexanderfoti]

I don’t mean to offend but, does anyone know for sure if there is a seat/steering position sensor that actually links to the start system procedure?


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Unfortunately, no link with the steering wheel/seat. It will start with both removed if desired.

 

[DSK]

Unfortunately, no link with the steering wheel/seat. It will start with both removed if desired.

Thank as always for confirming.


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[DSK]

UPDATE

So the owner called me after work, on Monday night, providing a detailed overview of what’s been tested, what’s been found, what’s been done etc. he appreciated my belt and braces approach and out of their 11,000 customers, I’m clearly not someone who wants a care repaired or working for free, but, in fact the opposite. Despite it being after hours it was probably an easy 35min positive chat without the feeling it’s a quick call and they need to go.

- floor repaired
- water tests confirm nothing coming in
- sills drained of all debris and they will check this at every service
- cloned ECU seems to be working well
- sunroof drains are clear
- front drains modified
- wiring and connectors ok
- they will fit that fuel pump relay for me today under my instruction
- they will fit my new Varta battery and terminal eyelets for my Nocco charger at the point of collection on Friday under my instruction
- the no start issue and no start signal from the ecu they appears to be resolved with the cloned unit.

I’m hoping this is just one of those unfortunate one off experiences, they said the car is genuinely exceptional and rare to see any car maintained like this one!

I’ll pick it up a Friday.


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[DSK]

Collected car today all well so far and all wood touched.

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[DSK]

Haven’t had a chance to use the car since collection (was started a handful of times by me that day) so, made time to take it for an hours jaunt on the motorway today. The car worked perfectly and with the Varta battery battery over the varta labelled MB one, the car starts with telepathy instantly, nice to have that again. I will make time to use it some more this weekend, but so far very good.


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[SL500+S500]

Fair-play to you. Sounds like it’s resolved.

I’m slowly coming to the conclusion that mine was running several simultaneous issues. One was the battery going bad, secondarily the fuel relay seems to make an audible click now at the first key position and thirdly I’m suspecting the key fob is slowly dying; given the EIS and ECU have been replaced/serviced. I’m at the point now where if it doesn’t start on the first bounce, I hold the fob in position until it eventually grinds into life And kicks the starter over.