security system wont let me fire the car ? on 1998 Ford Mustang

The car will crank but wont fire, its not a fuel issue because fuel comes out when i purged it, i called the guy i bought it from and he said the alarm was on it when he got it, its not stock and dont know the make of it, why wont it let me fire it up and what do i have to do to get it runnin again ?

Asked by for the 1998 Ford Mustang
Disable/remove this non-stock security system (if you know how) and try to start the vechicle. Or take to a security installation shop and have them disable it and try to start vechicle.
1 more answer
The battery may have gone out - check that. That is exactly what happened to my 98' when the battery died.