On the cylinder head there should be temp sensor close to the pump. This is to tell the cold start device that the engine is hot or cold. Look for a plug on the side of the head towards the rear or a spare hole where the plug may have been removed.
on the 250 there may have been a cast iron thing bolted to the head where the water temp thermo switch was mounted and the wires connected to it.
What is the model number of the injection pump ,on the little plate and the model number of the governor (on the rear of the pump) ?