Not having experience with a Trooper....but with many other cars...
most mechanical pumps for carb engines have 2 lines - one to tank, one to carb. inside the pump is a rubber diaphragm that when moved by the engine running pumps the gas.
IF this diphragm has a hole in it, the breather hole will leak gas...so you need a new pump.

Now, as to the 4 lines you say you have...
the only pumps i have seen with 4 lines are those that are helf fuel pump, half vacuum pump. (cars from the 50s have this as they have vac operated wipers, power locks, ect)

You say you are having problems...what problems?