So I bought I 2000 lincoln ls v6 with 181k about a week ago. When I went to look at it, the owner was having problems starting it. His friend who was a mechanic came and ran diagnostics on the engine and it showed zero fuel level in the tank but the gauge said 1/4th. We figured something was casusing the it to float at a quarter of a tank. Put afew gallons of gas in and it ran fine. I bought the car and went and filled it up and made the two hour trip home. Ran fine although the engine light was on(which he told me the engine light was on previously) after getting home I noticed that the car would start to stall then die when left idling, it also took a second to start every once in awhile. I was giving my mother a ride to pick up her car yesterday and when I dropped her off my car wouldn't start back up, it was at a half a tank. Went and got a gallon of gas and it started fine. Put in 6 more gallons and the tank read full. Looked at the fuel pump later that day and I really had a full tank and the fuel pump started fine also. So at that point I thought maybe the secondary pump was on its last leg. Well today I gave her another ride and I start at the gas station for some cigs and the car was havin problems starting back up. It would start and then die and then wouldn't start at All and it finally started and was running fine. It was just under a full tank. I'm stumped! Also right after I got home I went to autozone and had some codes pulled, they were p0401 p0171 p0174 I cleaned my egr valve and port and also my mass air flow sensor. I didn't notice any leaks in the vacuum hose leading to the egr valve either. I'm lost and I'm been trying to figure this out on my own, but I want to get everyone's opinions before I buy a secondary pump for no reason. I don't know if its a problem with fuel pressure or a pump. But I hope to be posting on this forum plenty in the future and looking forward to hearing all of your guys advice. Let me know if you need any more information from me! Thanks!