If you're referring to the Optical / Fuel Temperature sensor on the DS-4's top, front...
...this is a pin out and diagram I was able to locate w/o a more exhaustive search of my 97 manuals which, I seriously doubt, there's been any changes since the IP hasn't. The Stanadyne DS-4 manual I have didn't have any kind of schematic.
A = 5volt Reference
B = Pump CAM Sensor Signal
C = High Resolution Signal
D = Sensor Ground
E = Fuel Temperature Signal
F = Sensor Ground