Start/Stop Problem 2014 E Class

[Red C220]

2014 E220 Cdi Auto. currently 3000 miles

The stop start system has never worked properly from the day it's been collected. It's been into Mercedes who have told me there's nothing wrong with it and it's working fine, which up until yesterday I'd not been able to figure out.

However I've noticed a pattern as follows:-

Start car from cold and drive from Surrey to Norwich - ECO lights up yellow but never turns green once in the entire 140 mile journey. This has now happened every time on 6 journeys.

However, if I stop for any reason during the journey for more than 5-10 minutes then restart the car - ECO goes green almost immediately, and works relatively normally although still has some drop out.

If I stop for a only a minute or two it's hit and miss if this works or not.

I now realise why Mercedes can't find a problem. They pick the car up, drive it for a half an hour - it sit in the yard for a period of time at which point a mechanic starts it and everything works fine.

Any ideas what could be causing this so I can point the dealer in the right direction as until the "computer" says there's a fault nothing can be addressed?

 

[Rory]

I suppose you drive it there and, without turning the engine off, ask them to come out and see the ECO light is yellow.

Or leave it with them overnight for them to try themselves.

It won't hit the tested MPG figure unless stop/start works so perhaps you could gently suggest it's non-compliant?

 

[Red C220]

I suppose you drive it there and, without turning the engine off, ask them to come out and see the ECO light is yellow.

Or leave it with them overnight for them to try themselves.

It won't hit the tested MPG figure unless stop/start works so perhaps you could gently suggest it's non-compliant?

I'm struggling with them to be honest and I'm going to try a different dealer.

When I explain the above I just get a blank look and they explain again that "the computer" can't find a fault and until it does there's nothing wrong with the car.

I was posting in the vain hope that someone might have a similar issue and found that it was the Battery temp sensor or some equally simple part to replace to solve the problem.

 

[Rory]

I was posting in the vain hope that someone might have a similar issue and found that it was the Battery temp sensor or some equally simple part to replace to solve the problem.

I've certainly read, probably more with BMWs than anything else, that the system can appear to work very randomly. But as none of cars have it I haven't paid much attention.

 

[Dieselman]

If the battery voltage is below a certain threshold at the first start, the ECO system won't select at any point in the journey, until a restart.
Normally the battery is above the threshold so ECO engages either immediately or after a short while.

 

[Red C220]

If the battery voltage is below a certain threshold at the first start, the ECO system won't select at any point in the journey, until a restart.
Normally the battery is above the threshold so ECO engages either immediately or after a short while.

By engage do you mean ECO in yellow or Green?

It occasionally goes green, but it's so rare that it's fundamentally inoperable unless it's been on a longish run then left for 5-10 minutes and restarted.

In the 3000 miles the car has covered I'd be surprised if it had been green for more than 300.

Fuel consumption steadily getting worse, the last tank was 31.5 mpg (using fuelly not the OBC) and that included 50% motorway driving at a steady 60mph.

Dealer suggests poor fuel economy is down to "the way I must drive".

This last weekend I just did Surrey to Norwich and back. I couldn't break 40mpg, it's mid to high 30mpg on a steady motorway run.

 

[Dieselman]

If all is good, it engages and goes green.

My car normally goes green after about 300 metres.

 

[Red C220]

If all is good, it engages and goes green.

My car normally goes green after about 300 metres.

Our C220 cdi did that for 3 years so I'm used to how this should be operating. It would be green before I reached the end of the road.

 

[Dieselman]

I drove a brand new E250, still with all the cardboard linings inside, and it didn't go green at all in ~20 miles, the CLS was green almost immediately.

I suspect your battery isn't fully charged at start due to being faulty or a voltage drain, or there is a battery monitoring fault.

 

[cunny678]

I have a new e220 and notice it doesn't come on as often when the air con is on! Do you have yours on all the time? If so, once you have done a few miles tomorrow try turning it off and see if it goes green.

My economy is not great either. Struggling to hit 40 mpg in mainly motorway use! In fact in roadworks with cruise set at 50 it only seems to be doing about 50 mpg.

 

[E280wilson]

My E350 doesn't work when I have the a/c on.

 

[Red C220]

Hmm, I leave it on Auto all the time.

I have a return trip from Surrey to Manchester on Sunday, I'll see if the a/c makes any difference.

 

[Rory]

Fuel consumption steadily getting worse, the last tank was 31.5 mpg (using fuelly not the OBC) and that included 50% motorway driving at a steady 60mph.

Dealer suggests poor fuel economy is down to "the way I must drive".

This last weekend I just did Surrey to Norwich and back. I couldn't break 40mpg, it's mid to high 30mpg on a steady motorway run.

Random guess, but I wonder if there's an engine temp sensor fault such that the car thinks its cold - would explain overfueling therefore poor MPG and the stop/start not working?

 

[stevehg]

My air con is on auto, and my stop start seems to work in all but the coldest of temps.

Mpg seems ok for the way I drive too, which is not too economical. It's ~44mpg on display on a mostly motorway and ranges between 35-39 for city, a & B road driving. This for a 2014 e220 estate with remap. Sorry don't bother to check fill to fill mpg's.

cheers, Steve

 

[Red C220]

My air con is on auto, and my stop start seems to work in all but the coldest of temps.

Mpg seems ok for the way I drive too, which is not too economical. It's ~44mpg on display on a mostly motorway and ranges between 35-39 for city, a & B road driving. This for a 2014 e220 estate with remap. Sorry don't bother to check fill to fill mpg's.

cheers, Steve

Who did the remap and did it make much difference to the driveability of the car?

 

[cunny678]

My air con is on auto, and my stop start seems to work in all but the coldest of temps.

Just noticed on occasion when I switch air con on, it goes from green to Amber immediately.

As regards MPG, mine is supposed to do 64.2 combined!!!

 

[Fudger]

However, if I stop for any reason during the journey for more than 5-10 minutes then restart the car - ECO goes green almost immediately, and works relatively normally although still has some drop out.

Mine works just like this; I have air con on automatic too.

 

[Dieselman]

Hmm, I leave it on Auto all the time.

Just a question.
Why would you want the A/c on at this time of year?

 

[Spin_bowler]

Mine works pretty reliably, Rear heated window bothers it when chilly. If it appears reluctant to turn green I turn the air on off momentarily and then it seems to play ball.

 

[st13phil]

Just a question.
Why would you want the A/c on at this time of year?

Presumably for dehumidification reasons?

BTW, one of the parameters the ECO Stop/Start system uses to decide whether or not to be operative is whether the screen is likely to mist up if the engine is stopped, so it must monitor the humidity level somehow or another and that may explain why turning the A/C off affects it's operation?