1989 Isuzu Trooper RAN AND STARTED PERFECTLY. INSTALLED NEW BATTERY, WON’T START. CABLES TIGHT.
Does it have a factory alarm system? Lock and unlock both the driver side and passenger side door to try to disarm the alarm.
Even before the OP tries to disarm the security system, there is a very basic thing to check, namely the polarity of the battery.
While it may seem insulting to hear a suggestion that the battery was installed incorrectly, this does happen on occasion–sometimes even to those with good automotive know-how.
If the battery’s polarity is okay, then the next thing I would suggest is to check to see if a fusible link in the positive cable might have blown.
When you say it doesn’t start, does it turn over?
… and your keyboard’s caplock is stuck on.
This sounds stupid but did you take the plastic caps off the battery terminals before you put the cables on?
LOL! That’s actually very common too. A friend of mine did that.
That woold do it!!!