CAB AS 1587697 - Caterpillar

the engine is running at low idle speed, the temperature of an exhaust manifold port can be an indication of the condition of a fuel injector. Low temperature at an exhaust manifold port is an indication of no fuel to the cylinder. This can possibly be an indication of a fuel injector with a defect. Extra high temperature at an exhaust manifold port can be an indication of too much fuel to the cylinder. This can also be an indication of a fuel injector with a defect.The normal operating temperature of the exhaust manifold ports is approximately 390 to 520 °C (734 to 936 °F). All of the exhaust manifold ports should be approximately the same temperature. Variation of the exhaust manifold port temperature by more than 50 °C (90 °F) from the average temperature of all of the cylinders could indicate a faulty fuel injector.If the exhaust manifold port temperature of a cylinder is out of the normal operating range and a defect in the fuel injector is suspected, remove the fuel injector from the cylinder head.Visually inspect the fuel injector for any of the following defects:
Stuck rack lever
Bound rack lever
Stuck plunger
Plugged nozzle tip orifice of the fuel injector
Broken fuel injector springIf the fuel injector has no visual defects, interchange the suspect fuel injector with a fuel injector that is operating properly. Assume that a fuel injector is operating properly when the fuel injector's exhaust manifold port temperature is within the normal operating range.Start the engine and check the exhaust manifold port temperatures again. If the temperature of the exhaust manifold port with the suspect fuel injector is now out of range, the problem is with the fuel injector. If the exhaust manifold port at the original location of the suspect fuel injector is still out of range, the problem is not with the fuel injector but another engine component.