Strictly speaking there isn't a diesel engine/fuel ratio.
In petrol engines the fuel and air starts to mix in the inlet manifold and enters the combustion chamber at 14.7 parts air to 1 part fuel.
In diesel engines the entire volume of the cylinders are filled with air only and then compressed until it is red hot. Diesel is then injected into the combustion chamber. The amount of fuel injected is basically determined by the injection pump and thus receiving acceleration inputs from the driver.