Temperature of an exhaust manifold port, when the engine runs at low idle speed, can be an indication of the condition of a unit injector, low temperature at an exhaust manifold port is an indication of no fuel to the cylinder. This could be caused by an inoperative unit injector pump. Exceedingly high temperatures at an exhaust manifold can be an indication of too much fuel to the cylinder, caused by a malfunctioning unit injector pump.
Use the 1U8865 Infrared Thermometer to check exhaust temperature. The Operator’s Manual, NEHS0510, for the 1U8865 Infrared Thermometer gives complete operating and maintenance instructions for this tool.