I am making a fire extinguishing robot. Everything else is working just fine except the water pump. The logic pin to which the pump is connected is giving out a voltage of 5V in the presence of fire as expected (which indicates that the logic is correct) when checked with a multimeter. However, on connecting the pump, this voltage goes down to a few millivolts (not sufficient to run the pump).
Also, on connecting the pump directly to VCC (which is also 5V, and cannot be programmed of course), it works (which means that the pump is not damaged either).
So, my issue is why is the pump responding to VCC but not to the logic pin, even though the output voltage in both the cases is 5V.