MFI Simplification Project - Help wanted!

[Jim727]

Not the microswitch, Dave. The microswitch is the black switch depressed by the throttle linkage when the throttle is closed. I know there are some pix of it on the board somewhere.

I was referring to the wiring diagram (the SL33 diagram found through the MFI references thread)

For a 1969 E/S in checking the connections. It shows the RPM Transducer as Item 69 with its pin 3 connected to the "Time Limit Switch" as Item 70 on the diagram. The microswitch is item 73 on that diagram.

For a '71 the diagram shows the RPM Transducer as Item 11 with pin 3 connected to a collection of grounds. Hopefully, the forum will let me upload the '71 diagram (have "issues" with screen refreshes).

Diagram:
Legend:



Jim

[David E. Clark]

I'll admit to a brain freeze!

You are talking about the switch which keeps the enrichment solenoid closed longer than the 2 second time limit relay to assist with starting very cold engines. It's described briefly under Cold Start Solenoid above:

When the starter is engaged, an electric current goes through a thermal sensor located at the top center of the crankcase. This thermal sensor measures engine temperature. If the engine is cold, current is allowed to pass through to the Cold Start Solenoid which activates allowing an injection of raw fuel to be sent to the intake stacks.

Here is a picture of the thermo-time switch switch from this thread: cold start enrich '71E



Its function is shown in this diagram from the same thread (originally from the CMA manual).

© Dr. Ing. h.c. F. Porsche A.G. Posted here for educational purposes only.

[David E. Clark]

Please check out MFI simplification thread (1st draft) for a cleaned up version of this thread. Add your suggestions and I'll re-edit the thread with all the new information.