How to Test a Caterpillar Excavator Unit Injector

How to test a caterpillar 325C excavator unit injector

This step can help determine why the injector is misfiring.

(1) If you have not yet checked for the presence of air in the fuel, perform the inspection steps and

refer to the “Air in Fuel Test” section. CAUTION: ELECTRIC SHOCK HAZARD. The voltage used

by the electronic unit injector system is 90~120V.

(2) Remove the valve cover and check if there are any broken parts. Repair or replace any broken parts

found. Check all wiring to the solenoid coil. Check to see if the connectors are loose. Also check to see

if the wiring is worn or disconnected. Make sure the connector on the unit injector solenoid coil is well

connected. Perform a tensile test on each wire.

(3) Check for signs of oil leakage. Investigate the cause of the fuel leak. Repair oil leaks.

(4) For the single-piece injector cylinder that is suspected to be faulty, check the adjustment of the valve

clearance. Please refer to the “Inspection and Adjustment of Engine Valve Clearance” section.

(5) Make sure the bolts holding the unit injector are tightened to the correct torque. To check the

torque, loosen the bolts holding the unit injector. Tighten the bolts to the correct torque.

2023 CAT ET 2023A 2022A & 2019C Full Service Download and Installation Service

(6) Remove the suspected faulty unit injector and check for signs of coolant leakage. Leaking coolant

can cause corrosion on the fuel injectors. If the unit injector shows signs of leaking coolant, remove the

injector sleeve and inspect it. If the injector sleeve is damaged, replace it. Inspect unit injectors for

excessive brown stains that have spread to the injector tips. If excessive stains are found, check the fuel

quality. Refer to the “Testing of Fuel Quality” section. Replace the seal on the injector and reinstall the

injector. Check for soot accumulation on the surface of the injector seat. If soot accumulates, there is a

gas leak. The cause of the leak should be found and repaired. If the fault is a gas leak, there is no need

to replace the injector.

(7) If the fault cannot be solved, replace the faulty injector with a new one.