Hi, forum! Wonder if someone knows what to look for?

I've had a issue for a little while. Sometimes the car doesn't crank the engine. First I thought I saw a pattern that it wouldn't crank immediately after driving for a little while and the car and engine was being warm but that doesn't seem to be the case, at least not every time. Car is a R350 with Keyless Go. Battery isn't exactly the best but my CTEK charger has no problem with it and even if the battery is fully charged the problem can occur.

What I've seen so far:
It seems that it always starts/cranks cold (not 100% sure of this but I think so).
When I press the start button and the car will not start I don't hear any "tick-tick-tick" like when the battery isn't charged and doesn't have enough capacity to start/crank. Actually I don't hear any sound when trying to start when it won't start.
I can drive, come home, park the car, kill the engine and then try to start immediately and it might not start but probably 9 times out of 10 it will start.
If I drive for a shorter period compared to a longer period hasn't been a factor as far as I've seen.
If the car will not start I can try multiple times to no avail but after a while it might start again.
If I've started it will not die and it behaves as normal and there is no warnings, no engine lights etc. on the display.
When I press the start button (without pressing the brake pedal) I can hear the fuel pump engage (as it normally always do).

What I've tried:
Switched keyfob.
I have removed the start button and used the keyfob to turn.
Charged the battery so it's full.
I've pulled and put back the relays in the front SAM to inspect them (all look good, no corrosion, moisture etc).

Example from one time some weeks ago:
Left home, car hadn't been used for a day and it's cold outside, drove for like 15-20 minutes, parked the car, came back after 15-20 minutes, the car will not crank. Waited for like 45 minutes and suddenly the car cranked, went home (which takes 6-7 minutes). Tested to crank car immediately after parking at home and turning off the engine, car will not crank/start.

Another day I left home, drove for like 45 minutes, went home, parked, tested to crank the car directly after parking, car starts without issues.

 

Classic symptoms of starter going bad.

 

Really? Sounds "good" to have it narrowed down so quickly, hopefully not to complicated to replace?

One question though, shouldn't I hear the relay ticking or the starter trying spin (make some sort of noise at least)? When it won't start it's totally quiet, only thing I can hear is what I think is the fuel pump everytime.

Thanks!

 

When the starter goes bad, it just won't spin, especially when hot. If you were standing out in front of the engine while someone tries to start, you might hear solenoids and relays clicking. You definitely can't hear it from inside the car.

It was about an hour on a lift to swap out the starter. My starter did the exact same thing when it was dying. First it would start with slow starts when hot, and then afterwards it wouldn't turn over at all when hot.

 

Check if you have the EIS module that has some cold solder. I’ve seen videos where that causes a no crank. Opening the unit and soldering the 3 pins fixes it. Only obviously if that is, that your unit is not a different one.

 

Kingpin! Did you find a solution?

 

Co ask.

 

I think I had the same problem. Sometimes the it cranks and starts but sometimes it doesn’t crank at all. Seemed to have something to do with temperature because it usual I worked fine at first start but after little while the symptoms come. In my case the problem was the EIS. Looks like the EIS modules in Mercedes have common problem. There is a connector welded to the circuit bord inside that loosens up. It needs to be welded back but please do not make the same mistake I did. I welded the connector back but there are tiny circuits between the parts that need to be connected and it is very easy to make a short circuit. There are various videos on YouTube that explain how. If you are good at welding circuit boards, go for it but I recommend taking it to someone who can solder the part back without heating it too much and who can do it under magnifying glass or stereoscope .

 

 

Thanks for your response.

I saw something similar on YouTube too.

I appreciate you.

 

As stated earlier, this is a common problem accross the MB range for this era from A series to S. Have you scanned your car for codes? EIS codes will show up if this is your problem.

It's a pity the original poster never bothered to respond after requesting everyone's assistance.

 

I haven’t scanned the car yet because I’m in a wheelchair and only have BlueDriver.

But I’ll scan and report back.

Thanks.

 

I’ve finally gotten out there to scan and I do have the EIS codes amongst others.

 

Im not farmiliar with the Blue Driver tool or the status it shows for many of the codes listed. Does "Not Present" mean it doesn't/never existed or does that mean that it was a previous code that occurred? Most scan tools used the term 'Stored or Historic' to described an error code that occurred in the past but not currently present.

My suggestion would be to get a better scan tool such as a Launch X431 or similar.

You also seem to have some undervoltage codes. Is your battery and alternator fully operational? That means at least 12.0 v (engine off) and 13.7 v engine on. A small drop in voltage will trigger many of the codes shown on your list.

Have the battery and alternator tested as the start of ANY diagnosis. Once confirmed OK, Id getba better scan tool that is MB specific. Bluetooth style code readers simply can't pickup everything you want to see. Even the good ones dont sometimes.

Clear all the codes over multiple trips, scan again and lets see what you have then.

 

I believe that the “not present” means that there is no information or signal coming from a specific component. The same type of code came from my Icarsoft MB V2. I believe The EIS module sends a “good do go” type of signal to the other modules. I think the EIS module needs the same repair as mine did. But done by a profesional electronist.

 

I'm glad I came across this post because I'm encountering the same issue since several years. That is, starter works perfect when engine is cold but is weak or very weak when engine is warm.

From what I read above, it could be solved by changing the starter. Or do I have to do some soldering? ​​What is EIS and could someone redirect me to the YouTube video explaining the issue?

R500, 5.5l.

 

Several different components going bad can exhibit the same symptoms. In my case, a new starter resolved the intermittent no start when hot problem. For others, repairing/replacing the EIS (electronic ignition switch, the part the key goes into) fixes it.

 

[QUOTE=Prerna;8944735]I'm glad I came across this post because I'm encountering the same issue since several years. That is, starter works perfect when engine is cold but is weak or very weak when engine is warm.

From what I read above, it could be solved by changing the starter. Or do I have to do some soldering? ​​What is EIS and could someone redirect me to the YouTube video explaining the issue?


that doesn’t sound like the EIS problem. EIS problem is when you turn the key and it cranks only when the connector inside touches the electronic plate where it’s supposed to be soldered.

 

[QUOTE=AdyGheorghe;8944746]Thank you. Not sure to fully understand, is there a way to find out whether the EIS is concerned, how can I know when "the connector inside touches the electronic plate... "?

 

Sometimes when I turn the key to crank with engine hot, nothing will happen for a few seconds, and the suddenly it cranks but slowly.

 

I understand you don’t have access to a obd scanner. You should get one or at least for the moment have it checked for codes. The EIS module will not cause weak starter when cracking. Only the no cranking could be the EIS. You could have multiple issues. You should get a OBD scanner.

 

Sounds like a bad starter to me.

 

Thank you all, I've got a cheap obd Bluetooth scanner that I haven't used for years. Not sure whether it's capable to detect anything at all but will surely try soon and report.

 

Any news here?

 

It has been decided that I have a faulty ECU.