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Link thunder ecu pulses injectors when power is cut off to it

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Hey guys having a bit of an issue with a r32 gtr running a link thunder ecu , basically the factory GTR r32 platform has a 12v constant feed to an injector resistor pack which then splits to each of the injectors. The issue I'm having is when I first turn the car to accessories and power up the thunder everything works sweet no issues I can connect to the ecu make changes run the engine etc. As soon as I turn the key off and disconnect power to the ecu the injectors start firing like crazy you can hear them from inside the cabin. Has anyone ran into anything similar or know where to begin? Any help is appreciated

You need to have the injector power switched at the same time as the ECU. (or later). I usually power the Injectors and Ignition Coil(s) from an ignition switch. That allows you to power the ECU, run the starter even with the ignition off, and no fuel or spark will be generated. You can check for fuel pressure, capture the crank/cam signals etc.

To give a bit more info on top of Davids comment, on most ecus that have peak & hold injector drives such as the Thunder, your injector power must come from an ignition switched source. The effect you are seeing is a back feed through the clamp diode on the injector drive. On ecus with only saturated drives you can usually get away with injector power that stays live all the time. So this is why the Link GTR plug-in ecu can work correctly without changing the factory injector wiring where as the Thunder wont.

It looks like it should be easy to fix though. Simply move the power wire to the other side of the eccs relay.

Factory wiring:

Modified wiring: