car just shuts off

[Trspit1500@aol.com]

ok, I have a new problem that just started happening tonight.  While driving 
the tach goes to zero, the ignition light goes on, I tried stepping on the 
gas, but that has no effect.  After coasting to the side of the road, maybe a 
couple of seconds the motor shuts-off.  It starts right up and drives normal, 
then this happens again about every 5-10 minutes.  Any ideas of why this is 
happening.  I added prolong to my engine today, but I doubt this had an 
effect on it.  
Thanks
Mike
1980 spit