1982 spider will not start no fuel injection

If it cranks and cranks then finally starts and slowly picks up speed you may have a leaking fuel pressure regulator, unfortunately this truck has an injection system know as the "spider" and everything including the regulator is under the upper intake manifold so you can't see it leak. GM makes a kit that replaces the spider and poppet setup with real injectors and I think it comes with a regulator. Do this, find the injection test port left rear of the air intake remove the plastic cap then have someone turn the ignition switch on to prime the system then press the schraeder valve and notice how much gas sprays out, next prime the system again but this time wait 5 minutes then press the schraeder again and the spray should be the same if there's little or no fuel coming out replace the regulator and I advise changing the injection system over. I hope this helps. Take care.

Maybe a problem in the fuel pump circuit. Check fuel pressure with engine off, and key turned to on, not start. If no pressure, diagnose the pump circuit at the fuel pump relay. One terminal for the relay would be the power feed for the pump. The engine computer signals the relay on for 2 seconds with key on to prime the system, also signals during engine cranking.

Does the fuel pump run? The inertia switch, if tripped will prevent the fuel pump from running. If the pump runs but the car doesn't start than it's likely a problem with the fuel pressure regulator or the bypass internal to the pump.

Lets start with terminology. I am assuming the truck is newer than 1987 so you would have fuel injection. No carb.
If it is a vortec engine, either a 4.3 or larger, and built after 1993, it could have central port fuel injection. That style uses one injector and a spider of lines that go to each intake port. This is inside the upper intake manifold.
Vortec engines require more fuel pressure than engines with port fuel injection or throttle body injection. So the first thing you need to do is check base fuel pressure before and after you crank the engine. You'll need a pressure gauge to do it. Normal fuel pressure at idle for a port injected engine is 35psi and 60psi for a central pfi system.

Spray starting fluid into the air intake of the engine, if it starts and you have fuel pressure you have no injection or injector pulse as we call it. Check ECM fuse one and two for continuity if it starts with fluid..

The fuel pressure regulator is mounted inside the intake plenum. You'll have to take the top half of the intake plenum off and replace the fuel injection spider.

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spider injection under upper intake plenum is bad or the fuel pressure regulator is bad, it is mounted on the spider, main problem with these blazers until 2003

This fuel pressure regulator is a component part of the SFI (sequential fuel injection) assembly, sometimes referred to as "spider". It resides inside of the air intake plenum and is accessed by removing the upper half of the intake. 
Good luck and hope this helps. 
Most of the time when your having problems, it's most likely going to be the whole spider unit. GM has been know to have problems with this type of fuel injection system. 
Check the vacum line to the fuel pressure regulator at the back of the spider housing by the high pressure fuel line. You can see it just in front of the distributor cap and spider assembly.

The vortec motor has been known for the so caller spider assembly which is the fuel injection set up inside the intake manifold going bad.The regulator starts leaking wich puts extra fuel into the motor.If that is it you should change the whole assembly.