Help - 1984 Mazda B2200 Diesel

Hello.

I have a friend who will sell me his B2200 if I can revive it.

Several years ago it quit running on him. The shop he had it towed to 
said they couldn't get a replacement for the failed part. He got the 
truck back, unfortunately without the part. His recollection was 
along the lines of "fuel" and "solenoid." The missing part came out 
from behind the dash, to the right of the steering column. It plugs 
in to a six wire pigtail, the socket is rectangular, roughly an inch 
and a half by three quarters of an inch.

I didn't find anything on-line at some parts retailers that matched 
this configuration.

Anyone have any idea what I am looking for here? Maybe a long shot, 
but it would be a shame for this truck to go to waste. Everything 
else is in fine condition and just begging to be run on Biodiesel.

Appreciate any help.

Scott.