Fuel Injector: Testing and Inspection

Testing fuel injectors

Preceding work:
Removal and Installation of injectors

Fuel injectors test.

Rough leak test a) Connect removed injectors to tester. Bleed pressure line with shutoff cock open and union nut open. Following this, tighten union nut.
b) Shutoff cock open: slowly operate hand lever (4 sec./stroke) and build up pressure to max. 1.5 bar gauge. If a leak is detected at the injector, the injector must be replaced.

Test opening pressure See test data for new injectors.
See test data for used injectors.
Close shutoff cock. Flush through injector by operating hand lever rapidly several times.
Open shutoff cock and test opening pressure with slow movement of hand lever.

Precision leak test Close shutoff cock. Flush through injector by opening hand lever rapidly several times, open shutoff cock and increase pressure slowly up to 0.5 bar gauge pressure below the previously determined opening pressure, and hold. No drop must form at the injector within 15 seconds.

Chatter test, assessing spray pattern
Close shutoff cock and flush injector by operating hand lever several times (0.5 sec./stroke). Following this, reduce lever speed to approx. 1 sec./stroke. This must cause the injector to chatter. No drop should form at the mouth of the injector. No string jet should form. Unilateral, atomized jet formation within a total spray angle of approx. 35 is permissible.
See illustrations for assessing spray jet.

Test Data:

Tightening Torques In Nm:

Commercially Available Tools & Testers:

Note
- The opening pressure, chatter, the jet and the leaktightness of the fuel injectors must be tested using an injector tester.
- Before it is possible to begin testing the injectors, the reservoir tester must be filled and the tester bled. Only clean test fluid (i.e. Shell mineral spirits 135) should be used for testing.

Assessing jet
Damaged fuel injectors

Formation of Drops:

Pencil Shaped Jet:

Stringy Jet:

Good fuel injectors