Electrical or fuel supply problem?
 

My 560 SEL shut down yesterday on the freeway 15 minutes into my 17- minute trip. Would not re-start. Gas tank 3/4 full. First, the radio went out, then the instrument lighting started to dim, then the engine started to sputter, and finally the engine shut down over an approx. 3-mile stretch, and I had it towed the rest of the way. Today, I trickle-charged the battery for a short time, thinking it was the alternator, but I got the car started right away. Battery was not dead in other words. Thinking it was a fuel line/filter obstruction. I removed the gas cap and fuel came gushing out. I do not see a fuel leak, and the battery connections nd fuses seem fine.

After some searching on this forum, it looks like perhaps the fuel pressure regulator, or a clogged fuel filter. But how would that impact the electrical system? It's been raining crazy here the last few days - could this have caused a short? I know there's a short somewhere in the vehicle, because various instruments in the instrument cluster drop off at times, but I don't see how this could cause the fuel system?

Where should I start the diagnosis:rolleyes:?

Ok, took it out, and it stopped again - same symptoms. This time the engine won't turn over, so I'm thinking it might be the alternator after all. Any suggestions before I start buying and replacing parts?

Thanks!

Took the battery to Kragen and had it tested, and it showed 300-some CCA, but was supposed to have 978. Bought an alternator and charging the battery now. Will install tomorrow. Hopefully it was just the alternator.

Stalling problem
 

Those symptoms you reported are very similar to the ones I got when my alternator failed. A new alternator fixed it. :)

Yeah, those old S-Class use a ton of current from the battery. Not having a 100% good battery can get you in trouble in a hurry. Not having a good alternator can ruin a good battery very quickly.

Double check your main ground connections and make sure the battery terminals are pristine before driving very far on your new battery. Last thing you want to do is ruin a brand new battery. Also check the connections at the alternator. You could just have a bad connection.

Curious, does that model have the removable brush assembly, or is that just the older diesels?

-tp

Yes - seems to have been the alternator
 

Had the hardest time getting the pulley off the old alternator. Ruined a large hex key that I had here in the effort, but took it back to Kragen and they took off the pulley with an impact wrench and put it on the new on in no more than 10 seconds! Gotta get me one of those!!!! Anyways, they tested the old alternator, and although it was supplying more than pleny enough current, it failed the test three times. Some sort of "filter" or similar had probably failed inside the old alternator due to the high production of electricity I was told.

Got the new alternator and the now fully charged battery in, and got the family to a Christmas party in time. Will double-check the connections to the alternator tomorrow and re-test the battery just to be sure.

Not sure about the removable brush assembly - rebuilding is a little advanced for me just yet.

Thanks for your help on this!!