Pressure Testing Injectors

Once removed, the injectors can be tested for correct spray pattern, leakage, and correct opening pressure. Fig.5-26 illustrates an injector being tested with a hand pressure pump. If the injectors fail any of the pressure tests that follow, see Inspecting and Repairing Injectors, later in this section.

Fig. 5-26.

Injector installed on hand pressure pump. Volkswagen special tool (VW1322 or US1111) shown.

Check general injector performance using rapid, short strokes of the testing pump lever (4 to 6 strokes per second). Check that the injector sprays in an even, compact cone pattern and stops cleanly, and that it does not drip after spraying.

To check injectors for leaking, slowly press down on the pump lever to a pressure of about 110 bar (1564 psi). Maintain that pressure for about 10 seconds. During that time, no fuel should drip from the injector nozzle.

To measure injector opening pressure, slowly push the pump lever down. Watch the gauge and read the value when the injector begins to spray. Opening pressure specifications are given in Table c. Any injector which does not meet the specifications should be rebuilt or replaced.

Table c. Diesel Injector Opening Pressure