I have a 2002 C240.. Last year, it suddenly wouldn't crank. I got it towed to an indy who diagnosed it with a starter problem. Got it replaced with a refurbed Bosch unit and it started fine for a year.. Until a few days ago..

Two nights ago, it wouldn't start. Checked the fuse, and it is blown. I replaced it with a 20A one in the morning and it started fine. At night, again it wouldn't start. Checked the fuse, and it is blown again. I replaced it again with 25A and it started fine. Drove for 30 minutes. Turned the engine off, and tried starting again 2 more times and it works both times.

This morning, it wouldn't start. Checked the fuse and it is not blown. Swapped out a few fuses.. A 30A ones and another 25A fuse and it still won't start. I checked with a 15A fuse again and it blows the 15A fuse. It confirms that there is current going through the fuse. I changed it again and tried it several times. On maybe the 7th try, it doesn't crank immediately but after maybe 2 seconds it starts cranking and the engine roared to life..

Drove to work, turned the engine off, and tried starting again.. No problem. Let it sit for 3 hours and tried cranking again, no problem. I also checked the battery voltage, and when it is sitting it shows 12.4V. I also changed the fuel filter last week.. Not sure if it has anything to do with this..

I am at a lost here.. What do you guys think? What should I do or check for? I am scared of getting stranded now..

 

Fuse 52 blowing is common & needs to be 20A. Check fuses 31, 52 & 57 - all required to be in good order for start enable. Check starter relay. Is the correct starter motor fitted? Check all HT wiring & earth.

 

Fuse #52 should be changed from original 15A to 20A as per Mercedes-Benz. Don't be changing Amps on any fuse just to try to give it more juice.

Battery should be about 12.7V before start; about 13.6V at idle and about 14.2V at 2000RPM
What are your voltages? Key out - key in, navigate to mileage on display cluster, push reset button 3 times, you should now be in dyno mode with voltage displayed.

When was the last time you replaced your car battery? OEM?

 

https://mbworld.org/forums/c-class-w...t-process.html

 

I also changed the fuel filter a week ago.. Not sure if it has any effects..

 

I removed and checked fuse 31, 52 & 57. They seem to be fine. When I started after checking those fuses, I have an ESP error. Does it have anything to do with pulling those fuses? I removed the starter relay and checked the contacts, but don't really know how else to check it. What is HT wiring & earth? Where should I check?


I just checked again my battery.. It is around 12.5 to 12.7 before starting. At idle, it shows 14.5V. When starting, it dips to as low as 10.5V. Are these numbers normal? I am actually still on my original battery I think. Maybe I should replace it.

 

14.5V is way too high for idle, should be about 13.6V at idle.
What are you getting at 2000RPM,.... make sure car is in Park or neutral and rev the engine up to 2000RPM to get reading.

If your battery is original then it is over 10 years old! Check date stamp on battery top of battery terminal,.... stamped right onto the metal top of either -ve or +ve terminal. Week(or Month) with last 2 digit of year. Should typically be replaced with OEM Mercedes-Benz battery about every 7 years.

For ESP error, try resynching ESP by: Car in idle, turn steering wheel all the way to one side, then all the way to the other side,.... repeat a couple of times.

 

The HT cables are the thick wires that connect the battery to the car. You also have earthing straps from the car body to the engine/transmission.

Your regulator should cut in at about 14.2 volts. Agree with SRT that 14.7 is too high.

 

I checked the voltage right after starting up after the idle stabilizes below 1k rpm. It shows 14.5V or 14.4V. It is the same at 2k rpm too. Do you guys think this is a problem?

I forgot to check the battery date. I also have not checked the strap between the car body and engine/transmission.

I have resynced my ESC.. I had to do some errand today and the few times I started it, it had no problem.. I am still worried about getting stranded somewhere though.. The 15&20A fuses blowing and the fact that it wouldn't start with 25A fuse would point at the starter.. Do you guys agree? Any precautions I should take?

Also, how many times does the starter usually click before the car comes to live?

 

Like I said, it should be about 13.6V at idle (which is about 700RPM). 14.5V at idle is way too high,.... I'd check the voltage regulator of your alternator.

Make sure those straps are not heavily corroded or oxidized,... should also check battery terminal cables (sand down so its nice and shiny at contact points) read the manual with regards to disconnecting battery,.... before you disconnect anything

 

dont rule out the starter

I have a diesel lawn tractor had the starter rebuilt but a shop ive used alot and had problems for weeks finally got a NEW starter and all was well

 

Just to bring closure to this.. I had the starter replaced again and the car has been starting well for the past week.. Lesson learned, when changing starter ask the shop to use a brand new starter.. The price difference is not worth it.. I looked around also and found a shop that would lifetime warranty the part+labor for starter replacement.. Should have done this the first time..