We acquired spectra of 24 LMC PNe in the 1150--3000 \AA range in order to
determine carbon and other ionic abundances. The sample more than doubles the
number of LMC PNe with good quality UV spectra in this wavelength range, and
whose optical images are available in the {\it HST} archive. The {\it Space
Telescope Imaging Spectrograph} was used with a very large aperture to obtain
virtually slit-less spectra, thus the monochromatic images in the major nebulae
emission lines are also available. The analysis of the data shows extremely
good quality spectra. This paper presents the emission lines identified and
measured, and the calculation of the ionic abundances of the emitting carbon
and other ions, and total carbon abundance. P-Cygni profiles have been found in
a fraction of the nebulae, and the limiting velocities of the stellar winds
estimated. The total carbon abundance can be inferred reliably in most nebulae.
We found that the average carbon abundance in round and elliptical PNe is one
order of magnitude larger than that of the bipolar PNe, while elliptical and
round PNe with a bipolar core have a bimodal behavior. This results confirm
that bipolarity in LMC PNe is tightly correlated with high mass progenitors.
When compared to predicted yields, we found that the observed abundance ratio
show a shift toward higher carbon abundances, that may be due to initial
conditions assumed in the models not appropriate for LMC PNe.Comment: Ap. J., in pres
