A liquid fuel pump arrangement for delivering fuel to an engine comprises a liquid-ring pump including a motor driven bladed impeller rotor which is located eccentrically within a cylindrical bore of a chamber forming part of a hollow pump body structure. The hollow pump body structure also accommodates a motor-driven prime pump impeller which pumps fuel within the pump body structure to an aircraft or other engine. An inner end wall of the liquid ring pump provides the liquid ring with access to the liquid fuel within the pump body structure while an outer end wall of the liquid ring pump has an air/vapor inlet port through which the bladed impeller of the liquid ring pump during rotation thereof draws air/vapor and an air/vapor outlet port the flow of air/vapor expelled therefrom by compression of the air/vapor within the liquid ring in response to rotation of the bladed impeller being restricted by flow restriction means.