I am at the end of my rope on this one.  I bought the car from a used
dealer about a month ago and since then it has broken down twice on
me.  Both times, it does the same thing;  start up strong, turns over,
then immediately dies.  The first time it broke down we took it in and
they replaced the starter, battery and belt in the alternator and it
worked for about a week and then died again.  The second time we took
it in (to a different place) they said it that the security system was
fried.  They disabled the system and it worked again for about a week
and now it is doing the same thing again.  Meanwhile, I’m thinking it
might be an electrical problem, since our blinkers have been working
off and on intermittenly; however the hazards and everything else
works fine.  

I have gotten it started before by pumping the gas before starting and
then continuing to give it gas after it starts; I kept it at 1500 rpms
for a few minutes until it idled by itself.  Another time, I took the
air filter off, pumped the gas, and got it started that way, but none
of that is working. Any suggestions as to what the problem could be?