The fuel cap light was added on Ford vehicles for only a few years because it is redundant and only is the fault of the cap very few times. The reason that the fuel cap light comes on is because of a fault in the evaporative emissions system, specifically it is not holding a vacuum when the purge valve and vent valve are closed. Think of the system like a soft drink cup from a fast food restaurant, your mouth is the purge valve, the straw are the vapor lines, and if you poke a hole in the bottom of the cup your finger will be the vent valve. When the power-train control module wants to do a check up on the evap system it will command the vent valve closed and the purge valve open to pull a vacuum on the fuel tank, after it has pulled sufficient vacuum on the tank according to the fuel tank pressure sensor, it will close the purge valve and look at the fuel tank pressure sensor for a calibrated amount of time to ensure that the tank and lines are holding the vacuum. Now if the vacuum rises too rapidly, there is a leak in the system like a fuel cap loose, fuel pump o-ring leaking, vapor line broken, fuel canister damaged, vent valve not closing fully, or a faulty/damaged tank. To put your 2 symptoms together I would look for vacuum leak or a stuck open purge valve, this will cause an engine stall and an evaporative emissions problem.
Aug 9, 2019 at 12:17 PM
