There isn't any gas going to the spark plugs. It won't turn over and start. Is it a fuel pump or is there a fuel relay button. 96 900s

No. Replace the Engine control unit that was destroyed when you reversed the polarity to it.

why not bypass the fuel pump relay with a jumper wire / fuse and see if it will start that way

Rather then guessing as to what the problem is learn to test ! Check the electrical circuit , hook up a fuel pressure gauge , use a spark tester to see if it has spark . Do you like buying parts you don't need ? Other wise your better off having a qualified repair shop check it out .
Testing Electric Fuel Pump Problems with Voltage Drop Test

Fuel Pump Electrical Circuits Description and Operation
Test the fuel pump relay ,do you know what a relay is and how it works ? Ford fuel pump electrical analysis begins at 8 mins into the video .
Do you know what a wiring diagram is ? Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model and engine size. Under system click on engine ,then under subsystem click on fuel controls . Click the search button ,then the blue link . scroll down to diagram # 7 ,this fuel pump electrical circuit .

Test don't guess

Looks like you got spark, and gas in the throttle body made it fire: nice work.
Sounds like your fuel pump is out or the wiring is not turning it on. One way to be sure is to set a spare battery near the tank and hot wire the pump with jumper wires. Or if you have a voltmeter check for voltage at the fuel pump connector while the truck is cranking.. If the pump is working and getting gas to the engine, see if the injectors are pulsing. A good idea to check fuel pressure if the pump is working.

Make sure that the belt isn't extremely tight and they the belt tensioner isn't liked up by pulling in the belt. It should move and spring right back. Make sure engine isn't locked up. And please explain what happen with the vehicle. The fact that you replace plugs and wires and fuel filter for a car that's not turning is throwing me off. So right now we are going all over the place. But definite look at belt and tensioner I've seen a few times that a bad tensioner will make the belt wrap around tighter inhibiting the engine from turning.

If a starter is able to crank the engine but it won't start you usually have either an electrical or fuel problem. It's also remotely possibly that it's compression.If an engine has proper fuel, spark and compression, it will start when you crank it. So your challange is to find out which part isn't working right. Start with fuel. Spray a little starting fluid into the air intake while someone tries to start the engine. If it starts briefly when you're spraying starting fluid, you probably have a fuel delivery problem. That could be injectors, fuel pump, fuel filter, relay, fuse... who knows what until you check into it.If it doesn't start with starting fluid, check the spark. Pull a plug wire and attach it to a spare sparkplug and set the plug on a solid metal part of the engine. Have a helper crank the engine while you watch the plug. If you have a good spark, it might just be out of timing.In any case, you'll need to start isolating the problem. Find out which part isn't working then you'll know what to replace/repair.

If a starter is able to crank the engine but it won't start you usually have either an electrical or fuel problem. It's also remotely possibly that it's compression.

If an engine has proper fuel, spark and compression, it will start when you crank it. So your challange is to find out which part isn't working right. Start with fuel. Spray a little starting fluid into the air intake while someone tries to start the engine. If it starts briefly when you're spraying starting fluid, you probably have a fuel delivery problem. That could be injectors, fuel pump, fuel filter, relay, fuse... who knows what until you check into it.

If it doesn't start with starting fluid, check the spark. Pull a plug wire and attach it to a spare sparkplug and set the plug on a solid metal part of the engine. Have a helper crank the engine while you watch the plug. If you have a good spark, it might just be out of timing.

In any case, you'll need to start isolating the problem. Find out which part isn't working then you'll know what to replace/repair.

Does it have spark at the spark plugs. If it has spark is it getting gas. Try spraying a little starting fluid in it, does it try to start? Then it isn't getting fuel. Is the fuel pump running when the ignition is first turned on? Fuel pump relay, fuse, fuel pump itself. Just telling you some things to check so people can give a better informed answer.

If this is a sudden occurrence and nothing suspicious happened prior, you most likely lost either gas or spark to the engine. You need to check for both.

Do you hear the fuel pump in the gas tank buzz on for a couple of seconds when you turn the ignition key to ON? Unless the fuel pump turns on and puts gas under high pressure at the fuel injectors, the engine cylinders won't get gas to start. Correct fuel pressure is crucial to know if you have a fuel pump (or fuel filter) problem. If the pressure is correct, it is probably not a fuel problem but a spark problem, although there are less common instances where a fuel injector circuit may malfunction.

The ignition system not producing spark at the spark plugs is the other common problem of no starts. Buy a cheap spark tester at a parts store, plug it into one of your spark plug wires, then crank the engine over and watch for a strong blue spark. You might need a helper to do this. If you see a consistent spark, the ignition system is probably good, although you should probably check more than just one plug wire-sometimes one bad ignition coil in a coil pack will cause no starting. Good luck.

If you open your fuel cap and have someone turn the ignition on you should hear a buzzing noise in the gas tank for two seconds. That's your fuel pump. Also go to the pressure regulator under the hood, access the pressure tester valve, press on the valve and have someone crank the engine for one second. You should get gas coming out.