Fuel Injection System - 6.9L Diesel: Testing: Injectors

1. Remove injection nozzles from engine and install each nozzle in turn on an injector tester. Test the injectors using calibration fluid at room temperature. Bleed the air out of the tester by pumping the handle several times.
2. Slowly lower tester handle and note the pressure shown on gauge when injector nozzle opens. Normal injection starting pressure should be 2000-2150 psi (140-151 kg/cm² ). If injection starting pressure is below 1600 psi (112 kg/cm² ), replace injector.
3. Using the injector tester, apply 1900-1950 psi (134-137 kg/cm² ) to injector. No fuel leakage should occur at this pressure range. Slight wetting of tip after 5 seconds is ok. DO NOT  wipe tip of nozzle with fingers. If leakage does occur, injector must be replaced.
4. Operate tester using quick strokes while observing flow from injector return ports. A slight leak-off of 1 or 2 drops per stroke is normal. If a solid stream is expelled from return port, injector must be replaced.
5. Build up pressure in the injector tester to just below injection starting pressure. Quickly lower handle on tester and observe fuel spray pattern. Fuel should be uniformly atomized and should form a narrow cone projecting straight out of the end of the nozzle. See Fig 1 .

Fig 1: Injector Spray Pattern Injector must not drip when needle valve is closed.