both keys have chip for security , 1 is bad
its not your ignition its your crankshaft sensor that's the same problem i had.
If your 1999 Ford Mustang cranks but won't turnover you may have a problem with the starter, the solenoid, or the alternator.
Sounds like you have a dead battery.
ignition coil! mine did the same
There are several reasons why a 1996 Achieva engine cranks but will not fire. A few of the reasons could be a bad ignition control module, ignition coil pack, or a crankshaft position sensor.
Coil? HEI ignition system?
Would be in the distributer or the ignition module
check for spark at plugs,coil.check you are getting fuel check ignition condensor
"Check Engine" light comes on when you turn ignition switch on and should go off when engine cranks.
Your ignition switch is worn out. you will need to replace it.
It could be the ICM or the pickup module.
ignition starter switch