  In this paper we revisit the radio pulsar death line problem within the
framework of curvature radiation and/or inverse compton scattering induced
vacuum gap model above neutron star polar caps. Our special interest is in the
recently detected pulsar PSR J2144-3933 with extremal period 8.5 seconds, which
lies far beyond conventional death lines. We argue, that formation of vacuum
gaps requires a complicated multipolar surface magnetic field, with a strenght
$B_s$ much higher than the surface dipolar component $B_d$, and radii of
curvature ${\cal R}$ much smaller than the neutron star radius $R=10^6$ cm.
Such a multipolar surface field is also consistent with death lines including
the extremal pulsar PSR J2144-3933. Since vacuum gap models produce sparks, our
paper naturally supports the spark related models of subpulse drift phenomenon
as well as to the spark associated models of coherent pulsar radio emission.
