almost cranks but will not quite crank?

On further thinking could it be the oil pressure sensor is bad? If so, where is it and how do I remove it?

Okay, you say it cranks but doesn't crank? So, do you mean it turns over when you turn the key but doesn't start? Or does it start up and then shut off after about 3 seconds? If that is the issue, then the fuel pump likely isn't turning on when it should. That system works normally by the relay turning the pump on for about three seconds to prime the system. Then the engine turns over. If it makes oil pressure and actually starts running the oil pressure switch sends power to the fuel pump and it runs. That also acts as a fuel shut off in the event of the engine stalling or an accident that causes something like a roll-over, so the engine loses oil pressure. As soon as the pressure drops the pump shuts off. There are a couple common failures. The pumps and connectors and the oil pressure sender. A simple way to test is to run a jumper wire to the prime connector which is a red wire that is normally wrapped in the harness near the relay. Or if you go to the ALDL connector under the dash and find terminal G and connect 12 volts there, both bypass the relay (relay must be installed though) and oil pressure switch and powers the pump. So, if you can attach power there and the truck runs you know the pump is okay and the wiring from the relay to the pump is good. If it primes the system and tries to start you know the relay is switching and the ECM is turning it on so that wiring is okay. That leaves only the oil pressure switch and the wiring for it. To test it the easiest way you just buy the replacement unit and install it. It is under the distributor at the rear of the engine. The old one unscrews and the new one screws in be careful though, it is a tapered thread and it's very easy to accidently tighten it too far and crack the adapter. I normally apply a couple wraps of Teflon tape and then screw it in just tight. There is no tech spec on that just until it doesn't leak. Now if it runs you should be good.

Is this the oil pressure switch?

I went ahead and replaced the oil pressure switch and still need won't crank. I don't know what else to do.

Did you try bypassing the power to the pump yet? If it runs that way then there is a wiring issue.

No I haven't done that. can you give me a visual on what you mean by bypassing? I am a little lacking in that department.

You just need a chunk of wire to connect between battery power and the prime wire or the G terminal in the ALDL and see if the pump powers on and stays on and the engine runs. If it still doesn't start and run, then we need to continue.

That's what I am not sure if I get that I need 12v but where exactly do I get it from, plug one end of wire in G terminal and then where do I plug the other end into?

Anyplace with battery positive, right at the battery works.

Okay, I will have to try it in the morning I've been at it all day and I will let you know the results.

Okay, I ran a wire to the battery and G terminal with a negative result. so, now I am trying to find something in the wiring that goes to the oil pressure switch that is broken or not connected if I am understanding you.

Okay, if the jumper didn't work and the fuel pump was running it might be the ignition dropping out. The jumper was to discover if it was the common issue with the fuel system. Sounds like it isn't that. That means we have to discover if it is losing spark. For that a timing light or an inline spark tester would be handy.

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

I checked for spark, and it does have spark.

Okay, so as a recap. You get in, turn the key and the engine turns over, starts and runs for a couple seconds then shuts off? Or does it turn over and not start at all?

It turns over but doesn't start at all.

Could it be the distributor?

It's possible but not likely. I would get a timing light and test it.

I checked the firing order and the #1 plug Is getting spark so I don't know what to do, it's getting fuel, and I have eliminated the relay, fuses and still I can't help to think I am just not seeing the problem and it's right in front of me. If I have fuel and I have spark, why won't it crank? It turns over but just will not crank, so I changed out the battery thinking it wasn't getting enough voltage but to no avail. It's like something is prohibiting it and once I get it then she will run strong. If not the distributor, then what is next, I already am going through the wiring hoping I find a broken or in need of wire. I've been on this for over a week.

Could it be the neutral safety switch that's on the steering column?

I finally remembered to record it trying to cranky for you and watch until the end it cranks for the first time in 9 days, sounds sick, then shuts off.

That still sounds fuel related, with how it has to turn over smooth it isn't internal engine or ignition related. Neutral switch would shut off the starter. Try this, get a can of starter fluid, now have someone try to start it while you spray some into the air intake, remove the air filter for access. If you can get it to start and run that way then you need to look at the pump and it's connections, then use a pressure gauge to verify the fuel pressure is constant while cranking and that it holds pressure as it tries to run. The other item on these is the EGR valve. They can get blocked open and that causes a large problem when they try to start. You can remove it with the 2 bolts then look into the pintle area. With it off it should be fully closed. GM had an issue in the early 4.3s where carbon in the engine would build up and a chunk could get caught in the pintle and the engine would stall out and run like poo if you could get it started. The solution is to use a cable on a drill and run it into the passages on the intake to knock the carbon free and then start the engine to blow the stuff out. There are Clean-Screen gaskets that can help stop the problem if it is carbon. My 94 had it happen to it. Hearing how yours was trying to start caused flashbacks.

I took the EGR off and cleaned it, the button where you pointed in the picture is poking out, does that mean it is open or closed? Does it mean I can't reuse it ? Also do I need to replace the distributor,it cranked again whenever I took off the EGR but I shut it off because it sounded like it was giving birth to an elephant. I don't quite know what to look for as far as the condition of I pull the distributor out.

You should be able to see if there is any carbon in the EGR as it would hold the pintle off the seat and there would be a gap around it. Shine a light into the rect. port and see if you see light. If no light bolt it back on, but plug the vacuum line to it and then see if it changes it at all. There is a control solenoid that turns off the vacuum to it, if it went bad it could hold the EGR open. Bolting it back on disconnected would block the passage, if it now starts and runs you would look at the solenoid. If there is no change then we need to check something else. Like actual fuel pressure.
The issue isn't the distributor. It wouldn't cause this issue and instead it would either not run at all or it would be backfiring through the intake or exhaust.

No change with the EGR now clean and back on, wouldn't crank even with starter fluid. I even checked and rechecked the grounds and relays and fuses and wires. I'm at a loss and really close to taking it into the shop, I just need it fixed.

If it still acted the way it was in the video even with the spray it may be an internal issue. However I would still check the timing and compression. It's not common but it might have jumped time at the timing chain. That usually creates odd symptoms though, not just a hard and long crank like you have but backfires and pops which you don't have. It's also possible the PCM is acting up but unless you have an OBD I capable scan tool that is hard to check.

What's the easiest way to do the timing without a timing tool ?

Timing light on cylinder one and aimed at the balancer is the only reliable way. You can generally get one as a loaner tool if you don't have one.

Isn't there a way to set timing without a timing light?

Sorry there isn't, not to test the actual timing.

I've set the timing and still not cranking,no changes. Could a bad ignition switch be causing all this, I have a lot of play in the steering wheel and can't turn the key backwards like a regular one.

Also I no longer can get the codes by counting the flashes through putting a wire between A&B it was working but all I got was one then two flashes indicating 12 now it does not flash at all. Don't know what happened.

From the description your problem is likely a failing ECM. That would get you odd behaviors and now the lack of code reading. You might want to hunt up a scan tool that can do OBDI The Snap-On MT2500 is a good one for that. That would tell you much more than trying to read flash codes.

Here is some photos from underneath the truck, a sensor on the block and the other speaks for itself. How many things do I need to fix and could this be the problem? ?

I got the crankshaft sensor out and it was filthy, I cleaned it, and bench tested it and got a small reading from it but the problem is I think between the dirt and the messed-up wiring as you seen in the video that that was my problem. I have to put it back on and put fluid in that I lost, and then do I have to reset the timing or go straight to trying to crank ?

If you are using the same sensor there is no relearn, that is used when you change sensors.

I put the cleaned crankshaft sensor back on and still no change. I didn't mess with the other sensor and wonder if I should take it off and clean it? I included a picture of the one in question. I don't understand because at one point the truck actually did turn over and crank for a moment (I sent a video remember?) so it has to be something I did wrong between them and now. The codes are back on the dash, and it just continues to flash 12. Any thoughts?

Flash 12 just means it hasn't stored a code. If it was mine, I'd start at the basics. You know it turns over, so that's okay, you had it running before so it should have compression and be in time. So that leaves spark or fuel as the likely culprits. With the way it has progressed as it is getting worse, I would look at the PCM itself as being the item that is failing. It could be as simple as a bad capacitor in the PCM that shuts off fuel or ignition as soon as it heats up. I would probably proceed by using an OBD I scan tool like a SO MT2500 or OTC Genisys to watch the live data from the sensors that it can show and see if there is something there that gives a clue.

While I am waiting for my friend to bring the equipment you suggested over, I've been tidying up and double-checking everything thing. I only have a couple of questions I forgot about and while they might not be important, I'd still like the knowledge so one is this ground wire (I'm guessing) that is located drivers' side where the fuel tank is, and it appears one end is missing the nut. I've included photos, does this go to the fuel pump and if so, could it keep the motor not cranking? I heard the pump when I ran the bypass as you suggested. Also, the other photo is of the top of the gas tank that I just included because I had it. Again, thank you for your help.

While I am waiting for my friend to bring the equipment you suggested over, I've been tidy up and double checking everything thing. I only have a couple of questions I forgot about and while they might not be important I'd still like the knowledge so one is this ground wire(, I'm guessing) that is located drivers side where the fuel tank is & it appears one end is missing the nut. I've included photos,does this go to the fuel pump and if so could it keep the motor not cranking ? I heard the pump when I ran the bypass as you suggested. Also the other photo is of the top of the gas tank that and I just included it because I had it. Again thank you for your help.

That would be a self-tapping bolt. If you were to look at a new one, it would be tapered and have a triangular profile at the tip. Tons of them used on vehicles.