Truck been sitting about ten years when I bought it. Will not start unless I hold the front injector about 1/4" out of hole where it goes. Starts and idles good when hold in this position. Place injector in hole and will not fire at all. Weird one huh.

 

Welcome to the forum

I assume gas tank was drained and new fuel was added and a new fuel filter

Reads like air flow issue, or too much fuel flow, pulling up an injector adds more air to the intake and a bit less fuel

Try removing a vacuum hose from intake with injector in place, to add more air

Check fuel pressure regulator's vacuum hose for signs of gasoline, this causes flooding of engine

Disable fuel pump, unplug the fuel pump relay, the GREEN relay on the inner fender
Crank engine over a few times to drain fuel pressure

With injectors in place open throttle and manually add fuel to engine then try to start, see if you can keep it running by adding fuel manually if so air is not the issue, fuel is