The study aims to approach the performance of fuel injection system of diesel engines when using
biodiesel as an alternative fuel. Mathematical model is proposed to simulate the fuel path through
the injection system taking into consideration the compressibility effect, pressure waves in the
pipeline, fuel properties and the leakage through clearance of moving parts. The model is
compared with another experimental work for validation. The effect of biodiesel properties and its
blends on the injection system behavior are examined. The results indicate that, when using
biodiesel as an alternative fuel, the pressure waves propagating through the line diminished rapidly
compared with conventional diesel oil. The results indicate also that, when using biodiesel, the
leakage decreased because of its higher viscosity. As a result, the rate of pressure rise increases
and the beginning of injection becomes earlier. It is important in this case to retard the injection
timing to optimize the engine performance. On the other hand, the study shows that, the same
atomization degree can be obtained when transformed to biodiesel by raising the injection pressure
with certain ratios. These ratios depend on biodiesel blend percentage and compression ratio of the
engine.