Fuel injection system of an internal combustion engine

A fuel injection system of an internal combustion engine in which an exhaust gas purification catalyst, which absorbs nitrogen oxides in an exhaust gas when it is in a cold state lower in temperature than an activation temperature thereof, is arranged on an exhaust system, said fuel injection system comprising:

• a supply device that supplies to said internal combustion engine either a first fuel which inhibits a phenomenon in which nitrogen oxides are adsorbed to said exhaust gas purification catalyst or a second fuel which does not inhibit the phenomenon in which nitrogen oxides are absorbed to said exhaust gas purification catalyst;
• and
• a control unit that controls said supply device in such a manner that only said second fuel is first supplied to said internal combustion engine when said exhaust gas purification catalyst is in a cold state, and a change from a state in which only said second fuel is supplied to said internal combustion engine to a state in which only said first fuel is supplied to said internal combustion engine in then made before said exhaust gas purification catalyst subsequently rises in temperature to said activation temperature,
• wherein when said second fuel is supplied to the internal combustion engine, said control unit controls said supply device in such a manner that a change from said second fuel to said fuel is made when a maximum amount of adsorption which is a maximum value of an amount of nitrogen oxides which can be adsorbed to said exhaust as purification catalyst decreases to less than a lower limit value thereof.