I need to replicate the original coil signal to ECU -HELP

EDIS and Megajolt installation related topics. Be sure to review the <a href="http://www.autosportlabs.net/MJLJ_V4_vehicle_installation_guide">Vehicle installation guide</a>

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I need to replicate the original coil signal to ECU -HELP

Post by Jolyon39 »



Rover V8 with the very early "federal" injection system.

8 injectors + a cold start injector.

Low impedance injectors

Flapper air flow meter

Lucas 4CU ECU (earlier version of the 4CUX ECU found in early range rovers/landrover etc)

The original ignition sends a signal from coil negative to the ECU after each spark event

........ this is crucial because it tells the ECU it is safe to fire all banks and start fueling the engine. The signal is actually just flyback voltage through a resistor and this pulse is what the ECU looks for. No signal = no injectors firing

I am installing Megajolt with two high current, wasted Spark Ford Coils and an EDIS 8 controller. Therefore I am throwing away the original distributor and coil.


After installing Megajolt I need to replace/replicate the pulse off the original single coil negative to the ECU.

This signal is off the negative side of the coil and through a 6K8 resistor, then to an input pin on the ECU

How do I replicate the original signal off the coil negative (I think it uses flyback voltage) with Megajolt????????

Any suggestion on how to post an image of this circuit now that photobucket is gone???????
We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct. - Niels Bohr

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Post by brentp »


The tach adapter circuit specified in the installation guide combines the signal from multiple coil packs into one signal:
https://wiki.autosportlabs.com/MJLJ_V4_ ... back_pulse

This may solve your needs.

We also have a pre-made tach adapter device here that follows the design in the installation guide:

Hope this helps,
Brent Picasso
CEO and Founder, Autosport Labs
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