I have a 220D that sat for several years, but previous owner said it ran last year after compression starting. I have no glow plug light before and after pencil type glow plug upgrade from mercedessource. Motor spins fast enough and acts like it wants to start. I can smell burnt fuel from the tailpipe, but it just won't catch. When the starter knob is pulled out to the glow position I do see the dash lights dim a little. I've found a couple of comments about W115 220d's not having a glow plug relay. What else can I check to verify function of the glow plugs? I've bled the fuel system and believe the fuel supply is adequate. Troubleshooting suggestions are appreciated.