I have a Toyota Hilux 2.8 diesel 3l engine injector pump has great pressure on only 3 cylinders but number 4 is lacking pressure enough to make it miss , what can corse this problem

You didn't say but presumably the engine uses a DPA type or distributor type injection pump.

In this case the injector line pressure is governed by the condition and setting of each injector. If the break-off pressure of an injector is set to 80 atmospheres that pump element will produce a pressure of 80 atmospheres.

If one injector becomes "soft" and worn so the break-off pressure has fallen to 20 atmospheres for instance, or if the injector sticks open, the pressure generated by the pump will be either 20 atmospheres or virtually nothing.

When a conventional diesel engine develops a misfire, best practice is to ensure valve clearances and suchlike are in order, the compression pressure is good and then independently test the injector (and heater plug).

If everything is in order the pump should be removed for testing, repair and recalibration.