Intermitent starting problems

I have a 2000 Grand Marquis with about 35k miles on it. Recently I have been having intermittent starting problems with it. The first time the problem happened was after a oil change at Wal-mart back in Febuary 2009. (which I will never use again.) I have been able to get the car to start every time by cranking the car over several times. (sometimes trying for up to 30 mins) There have been a few occasions when I added gas treatment or a little bit of gas and it was able to start within 5 mins cranking it up about 3 times. Each time I had the problem there was at least a quarter tank of gas in car or more. Other times, I could start the car right up and drive to the store and within 5 10 mins of leaving, the car would not start but eventually started after trying to start it for a bit or adding a little gas or gas treatment. Other days the car will start up fine and drive with no problem. Any input or advice would be appreciated. Thanks!

Combustion needs three things: air, fuel, and a source of ignition (spark). Check to make sure those three things are making it to the engine.

I'd start by turning the key to ON (not start) and listen for the fuel pump. If you an hear it turn on for 2 seconds when you turn the key to ON, it should be okay. Next, check the fuel pressure at the rail with a fuel pressure gauge. If you have not ever changed the fuel filter, now's a good time to do so since they're under $12 most auto parts stores (I prefer Wix because they include new plastic clips in case you break the originals).

If fuel is getting to the engine, look for a lack of airflow. Does it start if you give it just a slight bit of throttle? If so, this indicates a problem with the Idle Air Control (IAC) valve.

Otherwise, your coils are not creating spark. This is usually related to the crank sensor not picking up the signal properly or a PCM ground problem.

It has been fine the last week or 2 started up drive somewhere shut it down start it up. New problem I seem to be having is it not starting after sitting till about 4 5 pm without driving it. Today its acting up. Would not start at all trying for close to 2 hours off and on. wonder if it will start tomorrow.

Turns out it was the fuel pump! Shop diagnosed it.