Its probably the alternator. Take off your alternator and take it to autozone and they'll test it for you for free.
If it's not the alternator--check the fuel relay and fuel filter.
I had that problem on my 1998 190E. It started by losing power on occasion and then more often, until it quit altogether. Each time the battery seemed to be drained. I actually carried a spare battery around for a while. Changing the battery seemed to correct the problem (for a while). I had the alternator checked and took it to 2 "Mercedes specialists". It actually was the fuel filter and fuel relay. It wasn't something the first 2 mechanics thought about. Hope this helps.
commentI've been having the same probs with my '91 190e, but only when i uuse the a/c. new alt and battery hasn't helped. I'll be changing battery cables soon.Could be the life of the battery has expired or the charging system is faulty or the vehicle has a draw on the system killing the battery when not running. Drive the vehicle to your local auto parts store. They will test the battery and the charging system at no cost. Battery is bad or something is draining it. Most places that sell batteries can check it. With it charged, disconnect it and see if it holds a charge. If it does, something in the car is draining it. Dead cell in the battery or something is on drawing power from the battery.
Change the abs motor.
Dead cell in the battery or something is on pulling power from the battery.
Dead cell in the battery requiring a replacement battery or something is on pulling power from the battery. Can be any light on the car or any relay.
You left the light or something on last night and ran out the battery or your battery died
Something is on drawing power. Can be any light on the vehicle or a relay stuck.
check you fuel pump relay
Possibly the alternator is defective and not recharging the battery. Or something is on, pulling power from the battery when the car is not running. Can be any light or any relay that is stuck.
on a 1990 cadallic sedan de ville after you cut the car off the blower keeps running killing the battery
If the battery is running down if it sits for a long period of time then either something is on that is pulling power from the battery or the battery has a dead cell. Check the under hood, glove box, trunk, & interior lights. Also check the brake lights. In rare cases it can be a stuck relay such as a power window relay. If it has a dead cell the only fix is to purchase a new battery. That one dell cell will continually run the battery down.
Weak alternator, dead cell in the battery, or something is on pulling power from the battery when the cars is not running.
Either the battery has a dead cell and needs replacing or something is on pulling power from the battery.