<Solved> I had this problem just now. I have a Q K 3.73 gear ratio Canadian made 2007 Mercury Mountaineer 4.6l V8 premier AWD. My advice is this. Get a scanner. you can rent one at an auto parts store and return it for a refund. Check the live data for 1. fuel rail pressure, 2. system vapor pressure, and 3. commanded purge percentages. It's one of the three. if any of those values are at zero %, change: 1. fuel rail pressure sensor under intake manifold, $119 at auto part store, $10 on ebay, look for a blue oring. This is a go sorenson. 2. vent solenoid, and canister if you cannot fill the gas tank with gas and gas just pours back out when its empty. it's not the canister unless it's this. it may be cracked and leaking but it's useable unless there's a p044x code and you can't pass emissions. no warranty at a store, $68 online. 3. 0% commanded purge; and the car should normally throw a p44x code, but if the if the pintle is broken and stuck shut it will over heat the fuel rail pressure sensor and throw a 1450 and/or 451. Remember on a ford, p0440-442 is the gas cap or purge, 443 to 446 is the purge to egr tube and rail or extra evs58 evap solenoid, some have two purge valves and an egr valve. 446 to 448 is the vent solenoid and canister. Usually. But wth about about a p1450 and a p0451. It's a vendor specific code and concerns circuitry. It specifically designates a blockage. you got to the shop and they want one of your kidneys like it's frickin indonesia or something. but you can isolate it to one area. The filler neck is not going to clog and you will smell gas if it's a leak concerning pressure. you can fix it for less than $150 yourself. And if there is any electrical problems it will be missing two or more percentages out of the three. For me, it was a purge valve and i could see the pintle, a white circular piece of plastic closing it off. you will also get an electrical code for a circuit malfunction. It can be confusing when it cuts off the purge valve to run the vent at max and vice versa because the egr has failed. but if it was a rail pressure sensor, it would have 0% rail pressure in a live data diagnostic and wouldn't start, but it would have vapor pressure. If it won't start it's the fuel pump and low pressure sensor or tank sensor on the pump. Ford have a red reset button. So, basically. it's easy to figure out. With one problem in the same area, it's most likely one sensor. I did a reset and it threw a different code. I'm glad it happened when it's cold. I recomend buying one from Quebec with a Q, K, in the manufacturer's label on the driver side door. One built in deerborn michigan is built after it's knocked over and amaged, all the parts, by eminem like 20,000 times a day. F@CK!!!!
