Cadillac: 1981 Cadillac Diesel, fuel injection pump, coolant line

Question
I have a 1981 Coupe deville. It has a 5.7 Diesel engine. I need an oil coolant line for it. Do I have to use a original metal line or can I substitute with something else? If so then would you happen to know where I could get one from? It also has a problem starting but I've replaced everything that I know has to do with the fuel. Do you have any idea what may be the problem?

Answer
he starting problem could be:

faulty GLOW PLUG CONTROLLER.

air in the fuel line due to a very small leak in the fuel filter.

A leaking fuel injection pump.

Look under the fuel injection pump and see if you can physically see any fuel laying in the area beneath the pump.