Fuel breaking/saving device for cars during coasting

Fuel breaking/saving device for cars during coasting, comprising:

• an automatic sensing power supply having comparison function and able to sense a preset standard value of R.P.M of an engine;
• a relay powered and controlled by the automatic sensing power supply to activate a fuel injector;
• a manual switch connected with a battery and a microswitch for controlling on/off of power;
• a normally closed microswitch connected with the automatic sensing power supply and the manual switch and activated and controlled by a linkage;
• and
• a linkage connected with a throttle shaft and activated and controlled by an accelerator pedal, whereby after receiving a message, the automatic sensing power supply compares the message with the standard value and judges whether the message reaches the standard value and then the automatic sensing power supply at proper time supplies power to the relay to make the relay decide whether the fuel injector should inject the fuel or break/save the fuel.