wayne1234

We have had our E550 4Matic for 4 years and it’s been very solid. This of the first thing that has me stumped I believe it’s 2 separate issues. First if I drive the car for 15-20 min and park and go into the store for example when I come back out to start the car it has a longer (about double) crank time, it’s never don’t this before, it always starts and doesn’t stumble or anything, it’s done this several times over the past few weeks even with different gas which was my first suspect. 2nd issue which has been going on for longer but seems to be getting worse is when I sometimes crank the car it almost seems like the battery is very weak /dead like it’s struggling to crank at first, I actually blamed the battery a few months ago and put a new battery in because it was several years old anyways and it did not change how it cranked. It does not always do this but it’s getting more frequent and doesn’t seem to have any rhyme or reason, sometimes it’s the first start, sometimes it’s a parking lot start like described above. Again it always cranks and starts but it’s getting worse and more often. I have a plug in WiFi Obd scanner no codes and it shows +13volts. And always has over 12v when I check it after it has sat. With this year the car has sat more and not been started in over a couple of weeks and the battery is not low. Other things I have done are plugs 20k miles ago recent filters. Etc. checked the battery connections and the ground, and the ground to the inner fender, thoughts? On the long crank fuel filter, fuel pump? I read about a possible check valve on a different Mercedes chassis? On the almost dead sounding slow crank is there a connection at a starter relay? Thanks

KEY08

Starter? Maybe getting heat soaked after driving.

bmwpowere36m3

Heat soak starting difficulty I'm thinking CPS or fuel vapor lock (less common I find). However these wouldn't cause a "slow" or labored start... just an extended cranking period.

Pull up the workshop menu, via the attached document. Use Up/Down cursor on wheel to select Vehicle data and press OK. I can't remember the order, but when you scroll thru the menu find the UB/IB display. UB is battery voltage and IB is current.

Take a video with the screen up while you start the car.... this will show the current draw and voltage. Post video or freeze frame at peak draw and lowest battery voltage. I would also confirm the voltage at the starter to ensure your getting 100%, verifying you don't have a bad ground or resistance somewhere in the circuit.

I'm thinking:

* Battery
* Poor power or ground connection (loose terminal or corrosion)
* Starter
* CPS (due to heat soak start difficulty)

Start checking the items off... might consider a better scanner that can pull MB-specific codes.

wayne1234

Here is the vehicle data video

markgm

The brushes on the starter are going: https://mbworld.org/forums/e-class-w...0-starter.html

Arrie

You don't mention what year your car is but from the video I can see it is the best cluster design MB did with 5 Barrels (like mine) so your car is coming to or has already passed the 10 year mark. (Air springs will be your next project). In the video your current goes to 102.4A, which is exactly what my car does. But this start is a normal good start so you should look at the voltage and amperage at every start until you experience a long crank as that could really show the problem in these numbers.

I had the same issue with long cranks but never experienced the weak feeling battery. It always cranked just fine but I got some long cranks. First I replaced the battery at the dealer and this helped for about a month or so but then problem came back. I got another new battery from Autozone (still in car) and again the problem came back in about a month. After this I replaced the starter and this solved the issue completely. Nothing else was done for the fix.

From my experience I think the battery change helped as the new batteries were fully charged as new but when about a month went by the "smart" charging system in the car allowed the battery charge go down some and then issues arise while starting when the starter robs too much amperage while cranking.

You can test for this if you don't think it is the starter. Charge your battery over night for a good full charge and then use the car normally. If it eliminates the problem for 3-4 weeks you probably have the starter going out. Your car is at age that this very likely can be the issue.

wayne1234

2010 E550 4 matic 126k Amg appearance has most options if that makes a electrical difference.

Arrie

Same as mine other than mine is RWD.

wayne1234

Yes that was one of the normal starts, but sometimes say every 3rd to 5th start it cranks like it is almost dead or has the long crank at this point and it’s getting more frequent. The weak/dead crank has been hit or miss for almost a year a new battery did Not correct or improve it at all, but again it getting more frequent, the long crank has only been the last 3 weeks or so and has done it approximately 6-8 times. I’m trying to head off a problem and avoid being stuck with a no start in a parking lot. Something is not right it didn’t do this before.

Left Coast Geek

next time you park, pop the hood but don't open it, then the next morning, without unlocking the car or opening the door, open the hood and use a volt meter on the jump start terminals (negative is a brass post on the right side spring/strut tower, and positive is under a sliding red cover. if your battery is fully charged, and temperatures are moderate, you should see about 12.6V give or take a 10th. if you see 12.1V, your battery is 50% discharged.

if your charging system isn't maintaining the battery properly, then even a nearly new battery can be dead, and these cars have really complicated (aka 'smart') charging systems.

wayne1234

Ironically I had left the car near this state, only I had the hood up. I checked the voltage and it was 12.34V I also removed the battery cover and checked on both sides of the wire as well, decided to try and start it again and got the slower crank I also pulled up the vehicle diagnostic and saw it dip down to 10.1V and -102.4A of course it jumped right back up..... is there a reset to the charging algorithm? I’m hesitant to say it’s the battery because it’s been doing this for over a year, and I replaced the battery a year ago when and it didn’t change anything.

KEY08

Put the battery on a trickle charger if you have one.

Left Coast Geek

or really, any car battery charger, preferably a modern 'smart' charger that won't OVER charge the battery. if it has an AGM setting, use it. I use a NOCO Genius 10.

CaliBenzDriver

Once you have fully charged your main AGM, go ahead and unplug the control wires from your battery sensor or simply drive with headlights:ON
unplug LIN Connector

This should safely peg your car voltage around 14V at all time. All the fancy smart charging will be disabled ( without battery data: no IC display!).

If a normalized voltage provides your car with consistent relief, you'll have identified the problem.

There are a few other causes for abnormally discharged batteries: CAN drain, ALT brushes...
🤞

Arrie

This picture of your starting condition shows 102.4A. Interestingly you can see this same amperage in the thread "low main battery" in post 154 from bmwpower36m and in the video clip in post 153 that is from my own S550 start. Just the other day I looked at my E550 and it shows the damn exact same current 102.4 A. This simply cannot be true. There is no way all four cars starters take the exact same load to a decimal.

All that tells me that the 102.4 A is not the actual current flow. It must be some sort of a maximum the system measures and displays.

I really think you have the issue with the starter. If you get a clamp meter and check the current from the battery cable while starting you can find the true load the starter takes.

I can then do the same to compare to healthy starters. I have two of them.

I always wanted to buy one of those clamp meters anyway...

bmwpowere36m3

I did a multiple starts with the E350 on my data logging trip and I checked the E550 tonight, each max out at -102.4A... so that's interesting. The refresh rate of the display is ~4Hz. Either the current is limited OR its as you suggest, a measurement/display constraint.

Here's the start on a '11 E550, the battery started at 12.45 VDC (car sitting for a while, hood propped open):

Left Coast Geek

102.4, eh? huh, thats 2^10 tenths of a amp, aka 1024, which written as a binary number is 10000000000 ... 1 more than 1023 which is the largest unsigned number that fits in 10 bits. I wonder if that Hyundai current sensing shunt thing uses a 10 bit ADC (analog to digital converter), measuring 0.1 amp units....

Arrie

Whatever it is, it is absolutely not possible for five cars now to use the exact same 102.4 A current draw at every start of the engine. I would say it is impossible for just one car repeat itself like that. The current reading must be maxing out.

Heck, my battery is a 900 CCA battery and in summer time it takes only 102.4 A? This simply can’t be true. Battery cables are with big cross section for a reason and 102.4 A does not come even close to that reason.

And you are a real “Real Geek” coming up with the binary theory, which could be (probably is) spot on. Would be amazing coincidence with the numbers if it wasn’t.

Clamp meter it is to be...

bmwpowere36m3

Measured 204.2 A on the E550 with clamp-on meter (Uni-T UT210D)... may have not captured the peak, as the auto-scaling of the meter takes a second to re-register.

Arrie

So it is double to what car shows and if you could catch the peak value it probably would not be exactly the same with each start.

This measurement could reveal the starter issue as I think the current is way higher with a starter going out.

Oh, just noticed in your picture the meter say 200 A AC/DC. Is your meter also maxed out?

Left Coast Geek

a '2000 count' meter goes to 204.8 amps, just sayin'.

Arrie

So it is maxed out, right.

bmwpowere36m3

Brain fart... its only rated to 200A. Gotta grab my other meter.

Arrie

I got a new meter for me that measures up to 1000 A. Got reading around 300 A. This was with hot engine. I will repeat with cold engine as it should be slightly higher current draw even in Summer time.

Now, thinking about winter this current pull may just double as oil becomes stiff to move around in the joints until engine warms up.

CaliBenzDriver

Your new clamp can be set to capture the IN-RUSH peak value !!

The peak would equate to the instant current before the engine decides to spin.

I'd guess 6 to 750Amps peak ✌️

This peak current is the truly destructive spike with all electric motors. The way around it is an electronic "slow-start" that ramps up current from zero, instead of down from high Infinite.