Looking at my 4JB1 manual, the thermoswitch for the glow plugs should switch ON (have continuity between the wire and the body) between 44-55* F (7-13* C) and switch OFF (no continuity) below 37* F (3* C).


1988 Isuzu Trooper LS
2.8l Isuzu 4JB1-TC intercooled turbo diesel
www.dieseltrooper.blogspot.com