My 2000 neon wont start

Nikki is the engine light on, are there any codes,have you had a tune up or any other work done lately.when you say it won't start when warm(do you mean engine will not turn over, or does engine turn and refuses to fire.
If I had to guess failing fuel pump, they tend not to build fuel pressure when ran a while(warmed up) and when left to cool build somewhat better pressure.
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Is Your Fuel Pump Going Bad
How do know if its fuel filter or fuel pump that is causing the problem
How To Diagnose Fuel Pump Failure EricTheCarGuy
http://www.clarks-garage.com/shop-manual/ts-01.htm#hot-start

Most likely starter motor sticking

The contacts and the plate assembly may be damaged. Better to replace it with a new one.

did the check engine light tell you there was a pcm fault or something else before you did the swap? Alot of things can cause a no start. A bad crank position sensor(CKP) cam position sensor(CMP) fuel pump. My brother-in-law did that to a dynasty and turned out to be a broken wire on the CKP circuit.

What year? First check for spark at any of the sparkplugs.If you have spark and fuel pressure then take the mass air flow sensor off and clean the small thin wires inside with a non-chlronated brake cleaner and let it dry for 10-15 minutes then re-install it and see if it will start.

If the headlights and dashboard lights are working but the vehicle still does not start, the ignition switch is most likely the problem. or a bad wire from switch. If your battery checks out, but the starter is still silent, it may be a faulty ignition switch. Turn the key to the on position (not all the way to start). If the red warning lights on your dash don't light up (and your battery connections are clean), the ignition switch is bad. If they do light up, turn the key to the start position. The dash warning lights should turn off at this key position (most cars). If you're not sure, turn on the headlights. When you try to start the car, the lights should either dim (a lot) or turn off completely. If they do, your ignition switch should be ok. If not, the switch will need replacement. check the wires to starter and see if you have power when car is switched on, do this first! good-day! if it cranks but does not start. check to see if spark and fuel, and check all fuses also.

the cam sensor and crank sensor are in the same wiring harness it may have shorted out the crank sensor you need to check to see if it has spark

any neon almost has a security system some times it will trip try using the key to un lock the door that will reset the system then start if nothing try the fuses under the hood one is bound to blow and wont let u start the car

2000 dodge neon cranks but wont start, but if i unplug the cam sensor it will run for a second

put a voltmeter on the the starter wires..if there is power then try turning the motor with a ratchet..it if wont turn then them motor is locked down