How to Test BMW Injectors

Written by chester rockwell
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Testing fuel injectors is an important procedure to perform to help keep the engine's fuel system running efficiently. Degraded fuel injectors can lead to a loss in fuel efficiency and gas mileage. In order to test the injectors, you will need access to an injector testing machine, which most mechanics have available in their shops. Many of these machines can also clean the injectors in addition to performing diagnostic tests.

Skill level:

Things you need

  • Resistance tester
  • Flow test bench

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  1. 1

    Remove the injectors from your engine so that they can be tested. They reside under the spark plugs, located above each cylinder head in your BMW's engine.

  2. 2

    Remove the inlet screens from each injector and rub out any corrosion using a rag or paper towel.

  3. 3

    Remove the O-rings and spacers that are on the ends of each injector by prying them off with your fingers.

  4. 4

    Using the resistance tester, check each injector's ohm resistance measurements. Inconsistencies between the test injector and the rest of your sample will indicate which ones may not be performing as well as the others.

  5. 5

    Mount the injectors into the flow test bench and pressure test each injector up to 80 psi. The flow test bench allows you to visually check which injectors are leaking or dripping during the test. You can also run the pressure test in reverse, with fluid spraying out of the injectors. This type of testing will flag out injectors that have an abnormal spray pattern, indicating that they may need to be cleaned or replaced.

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