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914World.com _ 914World Garage _ Help for the electrically unsure

Posted by: jmargush Apr 13 2022, 04:33 PM

I am in the process of installing a CB Performance Injection system with crank fire ignition.
This requires a module to run the Tach of off low voltage, so I have to buy a module to convert the signal form the ECU.

The instructions say I need a 12 volt power wire that comes form one side of the ignition switch to the tach.

Then I also need a wire that eventually goes to the ecu, I assume this would be the existing wire that drives the Tach?

Then a ground
Can anyone help me by telling me which wires on the back of the tach correspond to these functions?

I assume #3 BRWN is ground

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Posted by: Retroracer Apr 13 2022, 10:14 PM

Comments added around your text:

The instructions say I need a 12 volt power wire that comes form one side of the ignition switch to the tach.
red wire to tach

Then I also need a wire that eventually goes to the ecu, I assume this would be the existing wire that drives the Tach?
thats the black (black / purple?) sender wire that goes back to the relay board

Then a ground
that'll be the brown wire

hope this helps. The wires at the top portion of the tach are illumination and hi beam indicators - you won't need to touch those.

- Tony

Posted by: Dave_Darling Apr 13 2022, 10:19 PM

On the 914, the ECU does not drive the tach. (The 1.8's L-Jet injection does use the tach signal to tell it when to open the injectors, though!)

The red/white wire is switched power.
The brown is full-time ground.
The black/purple (look carefully on your black wire, there is a faded purple stripe!) carries the points signal to the tach.

The stock tach uses the open/closed signal from the points to move the needle. It is likely that is what the adapter uses as a signal as well.

--DD

Posted by: jmargush Apr 14 2022, 05:14 AM

Thanks so much guys. One more item to check off!