Diesel Injector Fuel Injector 0445120053 Bosch for Man Truck Diesel Engine

There are several methods of how to check the operation of the injector. Let's list them in order with a detailed indication of the algorithm of actions.

1. Checking by measuring resistance
You can check the injectors without removing them using a multimeter. To get started, check which injectors are installed on your car - high or low impedance (electrical resistance). This data will be needed to perform an accurate diagnosis. In order to check the injectors with a tester without removing them from the internal combustion engine, you need to adhere to the following plan:

2. Measuring the resistance of the injector winding
(1) remove high-voltage wires from injectors;
set the multimeter to the mode of measuring insulation resistance (ohmmeter) in the range from 0 to 200 ohms (depending on the technical parameters of the device, the upper limit may differ, most importantly, so that the ohmmeter can show a resistance value of several tens of ohms);
(2) turn off the ignition and remove the negative terminal from the battery;
disconnect the electrical connector on the injector being diagnosed (usually, for this, the mounting clip located on the block body is snapped off);
connect the test leads of the tester to the injector leads and measure.
High impedance injectors have insulation resistance within 11…17 Ohm, and low impedance — 2…5 Ohm.

If the value of the measured insulation resistance differs significantly from the specified value, this indicates that the injector is faulty. Accordingly, the nozzle must be dismantled and a detailed diagnosis should be made.

Remember that when checking injectors with a multimeter, you need to diagnose all devices one by one! So you can check which injector is not working.
It is important to know that the voltage to the injectors from the ECU is supplied in a pulsed form, not a constant one. Therefore, it is recommended not only to measure the resistance with an ohmmeter, but also to take an oscillogram of the impulse voltage transfer using an oscilloscope, so you can see what peak voltage it takes. The tester will show you only the average values.