W210 E320 almost won't start puzzle.
 

Went out for gas & car wash. Car started normally. Drove to gas station.

- Filled up (100%) and went to re-start.
- Engine barely turned, started but stopped when I took foot off pedal.
- Tried again, barely turned over.
- Fiddled with key and gear shift to make sure everything OK - Tried again - barely turns over.
- Turned key off and tried again - nothing - engine does not turn over.
- Again fiddled with key and gear shift and tried again - this time engine turns slowly and catches - kept foot down until I was sure engine would not stop.
- Went through car wash and then drove home.
- Stopped car in garage, then restarted no problem
- Tried again no problem.
- left car for an hour or so (lunch!), then checked battery voltage (12.15v) and then restarted, again no problem.
- checked voltage while charging - 13.97v. (bit low?)
- Sealed battery so can't check cells.
- Battery is about 3 years old.
- Checked connections and also connector voltage drop - all OK.

Any sugestions as to what might have caused this?
Could of course be battery but why just at this one time and then OK again?
Could it be something to do with overfilling tank? - probably not because engine turned over slowly.

Just to clear it up, what year is your W210 E320?

1996-1997 E320's have the 3.2 liter M104 straight six engine.
1998-2002 E320's have the 3.2 liter M113 V6 engine.

It's a '98
(1998-2002 E320's have the 3.2 liter M113 V6 engine.)

Any suggestions?

What should charging voltage be?

I think your battery is on the way out. The charging voltage is reasonable, so I don't suspect an alternator problem. But the resting voltage of the battery is quite low - should be closer to 13 volts for a fully charged lead-acid battery. From a quick google scan on battery information it appears your battery is less then 30% charged and the voltage is low enough that sulfation of the lead plates is occuring, which over time destroys the battery. Try a google search using terms like: lead acid battery voltage charge state.

- JimY

Hi Jim - You could be right!

Is that right?? On our boat, we have a voltmeter and three battery banks - They are usually just over 12v (on the hard to read analogue voltmeter). Must check our other cars as a comparison.

Did do a quick Google search, but will read further.

Thanks for the input.

Graham