Wont start new battery
Thread Starter
Junior Member
Joined: Sep 2019
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From: Miami
C300
Wont start new battery
Hello everyone, I was gone from home for 2 months and came back to a dead battery. So I got a new battery and still wont start??? Car drove and started no issues when I left. Car tries and tries to start but when you think its about to fire it doesnt.. Sound slow low a low battery but thats not the issue
Need my car asap for work
thanks
Need my car asap for work
thanks
Thread Starter
Junior Member
Joined: Sep 2019
Posts: 32
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From: Miami
C300
I do have a new battery charger just got one. Was only gone 2 months so cant imagine bad fuel. Its the 6 cylinder with 185 miles. I posted a video of it trying to start. It sounds like its about to then no, and its a slow start like it would be a dead battery but battery was just replaced.
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W212 MY'14 M276-3.5NA @75kMi
still slow crank
I do have a new battery charger just got one. Was only gone 2 months so cant imagine bad fuel. Its the 6 cylinder with 185 miles. I posted a video of it trying to start. It sounds like its about to then no, and its a slow start like it would be a dead battery but battery was just replaced.
You likely have voltage drop issue or a bad starter.
Are the new battery connections CLEAN & TIGHT??
DISCONNECT NEG side before dealing with RED connection... careful with 800Amp dead short across !!
Thread Starter
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From: Miami
C300
yes terminals are clean and tight.
I was thinking starter or fuel pump. Did you watch the video?
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
SLOW-CRANK... STARTER!
"Slow-crank" confirmed.
Fuel pump do cause "no start" but not "slow crank" - Needless to say you do need fuel rail pressure from pump, yes.
Use a $130 handheld scanner to help troubleshoot & save from not replacing a collection of good parts (read status, voltage and fuel pressure).
Of course do charge up your new battery... then if that crank begins slow: suspect STARTER.
Modern starters die without warning when one electric brush gets a hair too short.
> PLAN B:
USE A "GENTLE HAMMER TAP" on starter to shake brushes loose again... starts right up!
Last edited by CaliBenzDriver; Aug 6, 2025 at 05:27 PM.
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Thread Starter
Junior Member
Joined: Sep 2019
Posts: 32
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From: Miami
C300
Yes, I did watch your video...
"Slow-crank" confirmed.
Fuel pump do cause "no start" but not "slow crank" - Needless to say you do need fuel rail pressure from pump, yes.
Use a $130 handheld scanner to help troubleshoot & save from not replacing a collection of good parts (read status, voltage and fuel pressure).
Of course do charge up your new battery... then if that crank begins slow: suspect STARTER.
Modern starters die without warning when one electric brush gets a hair too short.
> PLAN B:
USE A "GENTLE HAMMER TAP" on starter to shake brushes loose again... starts right up!
"Slow-crank" confirmed.
Fuel pump do cause "no start" but not "slow crank" - Needless to say you do need fuel rail pressure from pump, yes.
Use a $130 handheld scanner to help troubleshoot & save from not replacing a collection of good parts (read status, voltage and fuel pressure).
Of course do charge up your new battery... then if that crank begins slow: suspect STARTER.
Modern starters die without warning when one electric brush gets a hair too short.
> PLAN B:
USE A "GENTLE HAMMER TAP" on starter to shake brushes loose again... starts right up!
I have a iCarsoft MB II Car Diagnostic Tool For Mercedes-Benz/Sprinter/Smart but I have no codes for starter, probably doesn't have that??
Im getting ready to buy set of car stands in 30 min, tomorrow morning I can take the belly pans off and try the hammer trick.
Just weird car worked no issues and not this ****.
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
I have a iCarsoft MB II Car Diagnostic Tool For Mercedes-Benz/Sprinter/Smart but I have no codes for starter, probably doesn't have that??
Im getting ready to buy set of car stands in 30 min, tomorrow morning I can take the belly pans off and try the hammer trick.
Just weird car worked no issues and not this ****.
Im getting ready to buy set of car stands in 30 min, tomorrow morning I can take the belly pans off and try the hammer trick.
Just weird car worked no issues and not this ****.
- Fuel rail pressure out from ECU
- Chassis voltage from both front & rear SAM's
- Drive authorization status from EIS
- All chassis faults as tell-tale sign of something bigger
If knocking on starter gets it going, it's only effective temporary for couple cranks. It confirms bad starter.
Last edited by CaliBenzDriver; Aug 6, 2025 at 06:43 PM.
Thread Starter
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From: Miami
C300
Using your iCarsoft scanner you can read :
If knocking on starter gets it going, it's only effective temporary for couple cranks. It confirms bad starter.
- Fuel rail pressure out from ECU
- Chassis voltage from both front & rear SAM's
- Drive authorization status from EIS
- All chassis faults as tell-tale sign of something bigger
If knocking on starter gets it going, it's only effective temporary for couple cranks. It confirms bad starter.
well I've had that scanner for yrs but only read the code faults then google to see what they are. I have no idea how to use it to read those things you mentioned lol
I'll try the hammer trick in the morning before its ten thousands degrees in Florida lol
Out Of Control!!
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Thread Starter
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From: Miami
C300
well I decided to try tonight with no luck with the hammer, I hit the solenoid and started. As you know its tight in there so not super hard but I thought hard enough. Now do I need someone trying to start it while I hit it or can I do this solo, hit it and then try to start it?
Tomorrow I'll get long screwdriver and use that with a hammer to make contact in different spots easier. I have the battery being charged overnight since its now down to 11 volts
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From: MA Coast
W204 2010 C300 4matic Sport M272
I watched the video.
Have you tried pressing the accelerator pedal to the floor when cranking? I say this because when my purge valve failed the engine would not start, would just turn over. Giving it gas made it start.
Have you tried pressing the accelerator pedal to the floor when cranking? I say this because when my purge valve failed the engine would not start, would just turn over. Giving it gas made it start.
Thread Starter
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From: Miami
C300
at this point I'll try anything before buying a part for $100 plus dollars
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W212 MY'14 M276-3.5NA @75kMi
STARTER VS LOW CHARGE
well I decided to try tonight with no luck with the hammer, I hit the solenoid and started. As you know its tight in there so not super hard but I thought hard enough. Now do I need someone trying to start it while I hit it or can I do this solo, hit it and then try to start it?
Tomorrow I'll get long screwdriver and use that with a hammer to make contact in different spots easier. I have the battery being charged overnight since its now down to 11 volts
Tomorrow I'll get long screwdriver and use that with a hammer to make contact in different spots easier. I have the battery being charged overnight since its now down to 11 volts
Try with a piece of timber as extension or the handle of another hammer...
-- Your fully charged battery is gonna help normal crank speed.
-- See your scanner for any faults reported about "low voltage" issues.
Last edited by CaliBenzDriver; Aug 6, 2025 at 10:32 PM.
Thread Starter
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From: Miami
C300
The starter brushes are located at the back end, near the power connection, inside the electric motor itself.
Try with a piece of timber as extension or the handle of another hammer...
-- Your fully charged battery is gonna help normal crank speed.
-- See your scanner for any faults reported about "low voltage" issues.
Try with a piece of timber as extension or the handle of another hammer...
-- Your fully charged battery is gonna help normal crank speed.
-- See your scanner for any faults reported about "low voltage" issues.
ok last night the hammer trick didnt work, this morning after charging the battery all night I put the key in and it started :-) let it run for a bit since it was running rough from sitting so long. Stopped and started it 5 times no issues
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G550
Off the shelf, there's no certainty about a battery's state of charge. I've had some that are fully charged, and some that will charge for a couple hours with a 10A charger. I always connect a charger after installing a new battery to be sure I'm starting out fully charged.
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W209, W124
Car batteries aren’t like Energizer Bunnies. You don’t assume they are useless once dead. Everytime they are heavily discharged they DO suffer damage and lose life. But frequently can be partially revived with a charger. Now that they are $200 it is worth spending $$ to have a charger handy.
And nothing to lose by trying.
And nothing to lose by trying.
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W212 MY'14 M276-3.5NA @75kMi
Next time you don't use the car over weeks simply disconnect battery (GND : "-" ) out of reach from chassis vampires.
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C300
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C200 w204
So no one is going to mention anything about the battery being at 11 volts . . . . . . no one?
chadzilla1, just for future reference when a battery is at full charge it is supposed to sit at around 12.6V, 12.3V is half charged, dead flat is at 12.00V. 11.00V is so flat that you lucky it even turned over.
These are just rough numbers to go by, and there are better ways to test batteries, but it's a good guide to go by.
chadzilla1, just for future reference when a battery is at full charge it is supposed to sit at around 12.6V, 12.3V is half charged, dead flat is at 12.00V. 11.00V is so flat that you lucky it even turned over.
These are just rough numbers to go by, and there are better ways to test batteries, but it's a good guide to go by.
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W204 2010 C300 4matic Sport M272
I bought a Noco Genius 5 charger to use every so often. I hard wired the harness in so I can put the charger in the engine bay behind the headlight and then close the hood, couldnt close the hood using the clamps. I dont have a garage and dont want to leave the hood open. I'll use it maybe once a month to go thru the conditioning process. I also hook it up when I use my foxwell obd scanner, though the MB manual says to use a 25-30 amp charger. I havent had any issues. I did drain the battery once when I didnt use the charger while playing with the scanner and had to use my battery booster.
