Spark plugs I cant seem to find the spark plugs for my sons 1996 pontiac sunfire,,, I thought I had found them but it turned out to be the fuel injectors,,, i think

Did you check the actual voltage reading to fuel injectors? I wondered about a voltage drop? Your fuel pump relay supplies voltage to both fuel pump and fuel injectors.
In the diagram, the gray wire is voltage and the other color is ground controlled by computer. Did you check fuel injectors, individually?I'd want to use a gage and check proper fuel pressure. Fuel--spark--compression--timing. There are other ways to get fuel in the engine besides fuel injectors, Just to see if engine will hit? There are safety issues, safety is your responsibility.

I have to ask, how long since a tune-up?
Are there any applicable trouble codes? To check codes yourself, at the least, you need an obd2 code reader.
If you lose rpm signal, there will be no spark at the plugs, no fuel injector pulse and other than the initial prime, probably no fuel pump activity.
The rpm signal comes from crank sensor. Don't replace anything unless your testing points in that direction. I don't know engine size?

did you check fuel pump relay also check your security system might be activated thinks its being stolen my daughters grand am does that once in awhile have to let it sit for 15 minuts with the key on on with out cranking it and then will start.

Check the injector relay or fuse.

Probably not. Depends on what the red line is.
Code 300 is a random miss - which could be a spark plug, coil, fuel injector, or other problem.

You will have to pinpoint what the engine is missing...
- Spark
- Fuel
- Compression

All three of these are tested when the engine is being cranked over. There are two way of checking for fuel. Fuel pressure and fuel trigger. Both are very important and must be present for the engine to start. Fuel pressure is self explanatory. You just hook up the gage and see what the reading is. Fuel trigger is check with a noid light. The injector gets unplugged and the noid light gets plugged in to the injector clip. With the engine cranking over, this light must blink. This is the signal to the injectors from the computer. You can have all the fuel pressure in the world, but it wont matter if the injector is not pulsing gas into the cylinder like it should.

Compression tester, spark tester, fuel pressure gage and noid light are all accessible at your local auto store. All three tests play a very important part in diagnosing a no start condition. Be extremely careful when doing these tests.

Sounds like you have a bad cylinder...
This could be due to a number of reasons...
No spark at one cylinder, due to a bad spark plug, coil, or wire.
No fuel due to a bad injector
Bad cylinder with low or no compression

Does it have spark at the spark plugs? Does it have fuel pressure? Does it have injector pulse? Does it have any compression?

If all the spark plugs are sparking and the engine timing is ok, then it can only be a fuel problem. You should check the fuel injectors.

Black smoke is from too much fuel, or a mis-firing of the spark plug. Pull all plugs to look to see if one is blackened. If so, this is your troubled cylinder. You can test each spark plug wire with a High energy spark plug tester. If that looks OK, then do a compresion test to see if the mechanical part of the engine seems good.