What would make you have fuel coming from tank but not out injectors on a 87 GMC vandura 5.0

The fuel injector, two wire connector, one is voltage, goes hot with the key on. The other is ground, controlled by the computer. The computer needs to see rpm signal to pulse the ground.
From the ignition module to computer, purple wire with white tracer carries rpm signal to computer, if no signal, the computer won't ground the fuel injectors, in my opinion.
If you have a digital multimeter that has a tach setting, it should react to a dc pulse on that purple wire with white tracer, engine cranking.
The usual culprit is the ignition module, but, I can't rule out other possibilities.
Engine cranking, do you have spark at the spark plugs?

The throttle body injector are turned on by a cam position sensor this is located in the distributor,