Most glow plug issues begin with a bad connection. Then the owners try to fix it and make things worse. Whatever you do, don't apply 12v to the plugs. Factory plugs were 5v. And don't use starter fluid. It can be used safely, but most people don't know how. It can damage heads and pistons. Your block heater is perfectly safe, they're great to have.
When cold, does your glow light come on? How long does it stay on?
Jack
_________________
'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.comIsuzuPup.com