The Glow Plug work better and last longer if the Carbon is reamed or otherwise cleaned out of the holes. Spoken of in the DIY Section.
"I am not looking for more work?" I do not see how work can be avoided.
With the Fuel Supply/Lift Pump you could test it (you would have to make your on connections for the Gauge/s); Rebuild it and hope that works or buy another Fuel Supply/Lift Pump and hope that works.
The easiest way is the more expensive and less sure way to trouble shoot; buy an new Lift Pump.
I believe your Pump is similar to the ones below.
Newer Lift Pump Repair with Disc Valves
95 E300D (606.910) Fuel Lift Pump Rebuild Question
606 Fuel/Lift Pump Rebuild
OM606 Fuel Pump Rebuild