Hi,
Have a '01 3.3 Grand Caravan. I get about 200 miles out of the first half tank. The second half, I am lucky to get 75 miles. By the time it hits E, I can watch it drop. Fuel leak? Any idea where?
Thanks,
Mike

 

The 01' Grand Caravan has a 20 U.S. gallon fuel tank. If the first half of a full tank lasts approximately two hundred miles than you are averaging about twenty mile per gallon, which is congruent with EPA fuel economy ratings for this vehicle. If the second half of a full tank lasts only seventy five miles, than your fuel economy would have suddenly and drastically changed to only about seven and a half miles per gallon. This is, at the least, the unlikeliest of all possibilities. The probable cause here is the fuel tank sending unit that relays the fuel level to the Body Control Module, or the instrument cluster itself. The sending unit in the tank converts fuel level into a resistance signal, that is then relayed to the BCM, and onto the instrument cluster. The sending unit has a float, much like that in your household toilet bowl, that rides on top of the fuel. The arm is connected to a potentiometer, which is a variable resistor. As the fuel level drops, the arm sweeps across the potentiometer and changes resistance in the circuit. I find it most possible that the area in the second half of the potentiometer is worn, and sending an inaccurate reading to the gauge, causing it to drop precipitously. To physically verify this before removing any components of the fuel system, simply fill the tank, drive until you are at the one quarter fuel mark, than refill the tank and verify the actual fuel gallons burned. It would take approximately fifteen gallons of fuel to fill from the one quarter mark. Any less than this and you know the level on the gauge is inaccurate. At this point, you would need to verify if the problem is the sending unit sending an improper resistance signal, or if the gauge is not responding properly. I do not have the resistance specifications available, but I believe that a full fuel tank has a 90 ohm resistance value, and an empty tank has a zero ohm value. You can verify this by checking the resistance value at the fuel tank sending unit connector with a digital volt ohm meter. If the resistance value does not match the known fuel tank level value, than replacement of the sending unit is called for. This will require removing the fuel tank from the vehicle. Good luck, and let me know if I can provide any more guidance.