start simple,

Check the tank screen (I know PO did it, but check it anyway)

Then the fuel filters of course. But also the fuel lines. They degrade over time. Especially with WVO. . .it literally eats the rubber.

Once the screen is good, and the filter and rubber fuel hose is good. Move on to the return check valve. On the later W124 cars, its a fancy banjo bolt, I think the W123's are the same. it goes right into the IP.

having it die out sounds like fuel starvation. So it "should" be a straight forward fix

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87' 300DT (Grey w/ red leather)
87' 300TDT (silver w/ palamino tex) SOLD

2012 VW JSW TDI (on tdiclub.com all the time "btcost")