How to Test a Caterpillar Excavator Unit Injector



How to Test a Caterpillar Excavator Unit Injector

 How to test a caterpillar 325C excavator unit injector  

12.2021 Caterpillar ECM ECU Flash Files Full Set Download 

 
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. 
 
 
 (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.