Fuel system problem

Noticed a constant humming sound coming from under neath the truck, could touch the inline fuel filter and feel the vibration. Changed the fuel filter, did not help, changed the HP fuel pump, started easier, but still humming, truck running fine. Then I removed cap from fuel reservoir to check filter, no filter in it. Since then truck starts easy, but then sputters and wants to shut off. The truck has a dual function reservoir, but the rear tank had been removed before I bought it. Can I just bypass the reservoir. Any help would be appreciated, Thank you