A fuel pump unit comprising a housing part (4) arranged between an electric motor (2) and a fuel pump (3). The housing part is provided with expansion joints for compensating thermal expansions or swelling of the material of the housing part (4). The gap between the impeller (6) and the housing parts (4, 5) of the fuel pump (3) can be kept constant by virture of the expansion joints, whereby the fuel pump (3) is essentially prevented from jamming especially when it runs dry.