Device for detecting a fuel supply system leak during an engine overrunning phase

A device for detecting a leak in a fuel supply system for an internal combustion engine during special operating conditions including an overrunning mode of the internal combustion engine, said internal combustion engine including injection valves (15) through which fuel is supplied thereto and said fuel supply system with a fuel tank (10), a fuel pump (11) and a fuel supply line (13) with or without a fuel return line (17) delivers the fuel via said fuel supply line at a fuel pressure to said injector valves (15), said device for detecting said leak comprising

• a pressure sensor (24) for continuously generating a pressure sensor signal indicative of said fuel pressure in said fuel supply line (13) or a differential pressure sensor (25) for continuously generating a differential pressure sensor signal indicative of a differential pressure between said fuel supply line (13) and said fuel return line (17) when said fuel supply system has said fuel return line;
• and
• an engine control unit (23) connected with said pressure sensor (24) to receive said pressure sensor signal or connected with said different pressure sensor (25) to receive said differential pressure signal when said fuel supply system has said fuel return line,
• wherein said engine control unit (23) includes
• means for detecting an engine overrunning condition,
• means for closing said injection valves (15) when said engine overrunning condition is detected;
• means for shutting off said fuel pump (11) when said injection valves (15) are closed;
• means for determining a pressure gradient (gradp) of said fuel pressure from said pressure sensor signal or a differential pressure gradient (grad .delta.p) of said differential pressure from said differential pressure sensor signal after said injection valves (15) are shut off;
• and
• means for comparing said pressure gradient (gradp) to a predetermined pressure gradient threshold (SW) or said differential pressure gradient (grad .delta.p) to respective lower and upper predetermined differential pressure gradient thresholds (SW.sub.o, SW.sub.u);
• and
• means for signaling a presence of a leak when said pressure gradient (gradp) is greater than said predetermined gradient threshold (SW) or when said differential pressure gradient (grad .delta.p) is less than said lower differential pressure gradient threshold (SW.sub.u) or greater than said upper differential pressure gradient threshold (SW.sub.o).