jkoogler

Let me start with the symptoms. First was a CEL for Lean Bank 1 and 2. I also had a problem that after driving the truck for a while and I would turn it off it would require me to put the accelerator to the floor to start back up again. Once it fired it would run rough for several seconds and then after driving would clear up. Eventually the truck would not fire sometimes like it was not getting fuel.
To remedy this I replaced the MAF and the fuel pump in the front tank. After replacing the MAF, I unhooked the battery for a few minutes to clear the codes and obviously resetting the computer.
Yesterday I drove the truck to work and after work fueled up. I had close to a 3/4 tank of gas in the truck. After driving home (about 10 miles) and 10 minutes of idling waiting for the wife I was down to just above a 1/4 tank of gas.
After getting home I checked for gas leaks and could not find any. What I did find was the vent hose for EVAP was pinched off and I repaired that.
This brings me to the question of why I am consuming fuel. Am I seeing the results of the PCM being reset? If so, how long (miles) does it take to re-learn?
Any help would be greatly appreciated.

1996 Ford F150
4.9 I6
automatic

Jay

joshtowal

First, I would confirm that you actually did use half a tank of gas. You're sending unit could be faulty. If you truly did use that much gas, you're getting about 1-2 MPG. Check the level on the other tank. It could just be returning the gas to it instead of the tank it's pulling it from.

jkoogler

The last portion was the answer. I had removed the rear tank in anticipation of changing that pump. The tank was trashed with rust, so i moved back to the front tank and changed that. I did not reinstall the old pump in the rear tank. After my wife sent a picture of fuel on the ground and talking to a coworker and a quick google search, I found there is a check valve in the pump. No pump= no check valve=full rear tank. As I am writing this I am siphoning gas out of the rear tank. Next step is to crimp off the lines.

Lesson learned!!!!!

Thanks for the help!
Jay