Does anyone have a systematic approach to diagnose a problem with the fuel system? I've got a starting problem that's been getting progressively worse, and now the 85 300CD just won't run.

Previously I would have to crank it for a minute in the morning (in FL and about 75*F in am) to get it started. Car would run fine until turned off. The longer the car was turned off the longer it would take to start during the day. A longer than normal start would occur when the engine was fully warmed up, so I don't think it's a glow plug issue, and all 5 were replaced 6 months ago. I suppose compression could be the problem, but I'm leaning toward the fuel system.

I've tried switching the intake and return fuel lines to elliminate a clogged tank screen issue. Have bleed the system several times at the filter housing, and the injectors getting air bubbles every time. And now I'm just stuck. There must be a factory trouble shouting tree for diesels. If anyone can share such an approach I'd really appreciate it.

Thanks,
Ken