My wife's venerable 368K mile 1984 300sd decided not to start and left her stranded. It cranks slowly but will not start and the dash lights flash while it cranks. Followed the normal systematic diagnostic approach; the battery was 5 years old, it was replaced with new,replaced the glow plug relay fuse and it has 12v power, the number 13 fuse was blown, replaced it, replaced the voltage regulator, wiggled and manipulated the shifter to see if it was the neutral safety switch, checked and rechecked all connections make sure they were tight and connected. Battery dies very quickly while attempting to crank, but it will crank indefinitely with jumper cables hooked to our other running 1984 300sd. I have an overload relay on order but would that explain why the car just stopped starting? Or is the Bendix on the starter drawing too much voltage out of the battery to let the car run? I am stumped any insight will be appreciated.