I think the problem is as follows (I may be wrong): The loop type plugs are designed to work at a variety of voltages since the voltage drops as the current goes from plug to plug. So the number 1 plug (nearest the radiator) gets a lot less voltage than the #5.
The pin type are designed to work at 12 volts. So the first few are working because they are at 12 volts or pretty close. The latter ones are not working because the voltage has dropped too low in the series wiring for them to function.
I'd put the loop type plugs in and see what happens, or get the kit that allows you to rewire with the appropriate electronics to put the pin type in.
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