Here's what I would do. I'd rig up a bottle of diesel fuel in the engine compartment, running input and return lines into the bottle. I'd run it on that system for a while and see what happens, If it runs ok with that system, the problem is not the IP but something in the fuel delivery system. If it didn't start and run right on the alternative system, I'd check the lift pump before condemning the IP.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13