Air Flow switch for fuel pump control
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
Air Flow switch for fuel pump control
I have not seen any discussion of the use of an airflow switch in the intake air stream for disabling the fuel pump if the engine is not running. CIS K-Jetronic systems use this method. What would be a source for such an airflow switch?
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john.p.clegg
Good question -- as I think I understand it, MS provides a ground for the fuel pump relay control for normal operation, then UN-grounds it when MS gets no tach signal.
For a CIS-equipped 911, the existing fuel pump circuitry can be reused in its entirety. The existing airflow sensor switch's wiring can be connected to the MS fuel pump signal. Or, an airflow sensor can be installed in the MS setup and connected to that same existing wiring to provide a pump shutoff that is independent of MS. That is the method I am exploring. And yup, an airflow sensor/switch is one more mechanical device that can fail ...
For a CIS-equipped 911, the existing fuel pump circuitry can be reused in its entirety. The existing airflow sensor switch's wiring can be connected to the MS fuel pump signal. Or, an airflow sensor can be installed in the MS setup and connected to that same existing wiring to provide a pump shutoff that is independent of MS. That is the method I am exploring. And yup, an airflow sensor/switch is one more mechanical device that can fail ...