Something is being overlooked. Your van uses a leak detection pump to pressurize the fuel supply system to 2 psi, then a pressure sensor watches for a leak. If the Check Engine light hasn't turned on, there is no external leak in the tank or emissions systems, but the fuel supply line has pressure up to more than 45 psi. If a leak was in that line, it would dribble gas while you were driving and for maybe a minute or two after you stopped the engine. The leaking would stop once the pressure was gone, so you would have to check for leaks under the vehicle while the engine was still running or right after it was stopped. The additional clue would be a very long crank time before the engine started running. That pressure in the line should stay there for weeks when the engine isn't started regularly. If the pressure bleeds down from a leak, it can take a good 5 to 10 seconds of cranking before the engine starts.
Based on what the oxygen sensors in the exhaust system report, the Engine Computer can only adjust fuel delivery by plus or minus about 10 percent. With ten percent extra fuel, the engine will run very rough and there will be black smoke from the tail pipe. That will reduce fuel mileage to around 20 mpg. Even a leaking fuel injector, which Chrysler has WAY less trouble with than some other manufacturers, can't kill the fuel mileage that badly.
One thing they have had some trouble with is leaking o-ring seals between the fuel rail and injectors. The fuel might collect somewhere where it vaporizes and blows off while you're driving, but the typical complaint is a bad fuel smell coming through the vents into the passenger compartment.
I don't mean to dismiss the issue, but you might watch to see if someone is siphoning your fuel. The obvious clue is the fuel gauge will be at a different level in the morning than it was the night before.
Tuesday, May 10th, 2011 AT 8:08 AM