Wont start somtimes. cranks over but no fire.

http://www.fordobdcode.com/p0365-ford http://www.fordobdcode.com/p0340-ford https://www.autocodes.com/p0420_ford.html
P0016 Ford Crankshaft Position Camshaft Position Correlation Bank 1 Sensor

Some vehicles it's normal for the starter to stay engaged after releasing the key , till it starts .

Causes can be numerous so here is some reading material which may help you track down your particular issue..........
Crank No Start

Can't be done online. You need experienced help to go through crank position sender, cam position sender, various relays, fuses etc. Can you hear the fuel pump running? It will only run when cranking and running , it won't run with just key on to prevent fire in accident.

Check starter solinoid

Listen for the fuel pump when you first turn on the key to the run position. If you hear it then spray a small amount of starting fluid in air intake while someone tries to start it if the engine fires then most likely a Crank Position Sensor. The CPS controls your injectors.

Your crank position sensor is bad. Check it for voltage with the key in the on position. If the crank sensor is not working the car will not start.

DDDD

When the key is held in the start position for .4 seconds. The pcm/ecm has a start timer, it will crank until timer is timed out even though you release the key. That is normal. I don't know how long the timer runs?

As far as vehicle starting, check the basics. If it cranks good but won't start, have a helper crank it while you check for spark at the spark plugs. If spark everywhere, use a gage and check proper fuel pressure. Also, check fuel injector pulse. Any applicable trouble codes? I can only help with testing.

no fire in the cranking position but fires upon releasing the key from the start position to the run

The solution to this problem was simple, embarrasing and frustrating. The dome light was left on, and discharged the battery....enough to prevent the ignition from firing apparently. I did not suspect this, because the starter would turn the engine over very well, for a long time, and would do this repeatedly. In all my experience, I have never seen an engine spin that well and not start. According to the dealer, the voltage was too low for the ignition to work. While I do not know the exact threshhold where the voltage is too low to crank, I could have detected the condition by checking the voltage at the battery while cranking. It should have been significantly below 12 volts, indicating a low battery. The tow truck driver who picked it up simply used a portable battery to jump it off and cranked it with no problem. The symptom of the starter continuing to run after releasing the key is new technology with computerized controls, and is normal nowdays. You don't really notice this because the engine usually fires so quickly that it is undetectable.

Try the fuel injection relay they are located under the hood. They blow out every few years on my Volvo. The car starts to quit all of the sudden. It is either red or green colored. It is located in the fuse box under the hood.