1989 Isuzu Truck Fuel pump replacement

if you have the 4ZD1 motor than the intake must be removed, if you have the G180Z or G200Z motor than the distributor will need removed to replace mechanical fuel pump.

Why must the intake manifold be removed to replace the fuel pump on the 4ZD1 engine? I wish to understand how it works.

because the pump is mounted underneath the intake, you have to remove intake to gain access to the fuel pump..