I have a 99 Ford Taurus, 3.0 Lit. For the last week or so, when the car sits idle for a long time (e.g. over night) when trying to start, the starter motor cranks nicely but engine will not start, pumping the gas pedal several times finally gets the car going. After that the engine runs very smoothly the whole day. Even after shutting it off for several hours , it has no problem starting up. It seems that being idle for over a long time (such as over night) causes the issue. I am wondering if there is an issue with gas pump or whatever mechanism that creates the vacuum to suck gas into engine for the initial engine startup.
Another very strange issue that might be related to gas pump is, if the gas tank is over filled (way over the full) then every so often the engine will start cutting off (hesitating and as a result jerking) like for a second or two and then it is runs fine. Once the gas level is at just below full the problem completely disappears and engine runs fine.
Any advise will be greatly appreciated it.