bought 2005 e500. No battery under hood. big one in trunk. It had batteries replaced. Both now in trunk? Not starting so want to charge both. Do not see it.

Box where backup battery should be is empty with sticker for it being in trunk but do not see it there. I assume car should start without it. Turns over easily. Charged main battery without disconnecting. I assume backup battery has to be separately charged?

Not a fuel pumps problem? Flywheel position sensor defective?

 

Little battery was not visible in dark . Where it is supposed to be. Looks new and clean and 12v+. FLAMM. Only for brakes? And should not interfere with starting? Box for air filter; not battery.

Starter runs strongly but no gas or ignition. Main battery fine. Replace both angular position sensors? With 2 fuiel pumps is one enough to allow starting?

 

it is next to the windshield washer reservoir filler, and underneath the cabin air-filter box. It provides electrical resiliency, in order that the brakes still work if the main battery fails. There are ample other discussions on the topic of batteries on this W211 part of the MB forum, including how to find and change the batteries. Have you read those threads? Try this one for a start.... https://mbworld.org/forums/e-class-w...-workshop.html

 

OZUSA: Fine info and reference. Battery looks new and is about 12.5v. Apparently gets charged o.k. Is o.k. to connect charger to main battery without disconnecting
anything?

I was told to replace crank and cam position sensors with MBZ ones on this 90K miles car for reliability. And might fix starting problem.

 

All ok with batteries, and now starting after checking fuel pumps relay in trunk fuse box. New $15. and back to instant starting and running. I expect with 2 fuel pumps if one quit other would keep car running; and are generally long lasting?