84' 190D has a tough time starting. It's got new fuel filters, a new glow plug relay and new glowplugs. Also the glow plug indicator on the dash glows before restarting. Any help would be appreciated because I'm about to call BS on my mechanic who supposively changed the plugs in July

 

It's possible they put in cheap glow plugs that could have failed by now. I'd check resistance and confirm plugs conditions.

 

Went through similar issue on '87 300TD. Glow plug light lighting up as normal, but running he battery down trying to start the engine. Replaced glow plug relay to be sure, plugs measured "good", no obvious electrical problems, still no fix. Found a very small crack on a rubberhose fuel line feeding the first fuel filter, replaced the hose, starts right up after "glow".