Dom Posted April 15, 2021 Report Share Posted April 15, 2021 Hey guys, I am new to this forum, so let me introduce myself: I am an automotive engineer form Austria. Currently a friend of mine and I are wiring up his stockcar with a Thunder ECU which is about 2.5 years old Thunder (sorry I currently do not have the S/N with me). We wired the injectors like they are supposed to be wired and as soon as we plug them in, they are triggered and fully opened, altough the engines is stopped. What could be a possible fault for this? Thank in advance, BR Dominik Quote Link to comment Share on other sites More sharing options...
Adamw Posted April 15, 2021 Report Share Posted April 15, 2021 That would only happen if the 12V supply to the injectors was live all the time. The injectors need to be powered by a relay that is only live when the ignition switch and ecu is on. Quote Link to comment Share on other sites More sharing options...
Dom Posted April 15, 2021 Author Report Share Posted April 15, 2021 So if the ECU is off it connects all injector deives to ground as this is its power-off state? And when the ECU is active it deactivates the injector gnds? We wired it with a main relay. The ECU is switched on and all of the 4 injectors are opened constantly. Both the 12v supply and the supply to the ecu are switched by the same relay. --> injector test is not possible as they are opened constantly. Br Dom Quote Link to comment Share on other sites More sharing options...
Adamw Posted April 15, 2021 Report Share Posted April 15, 2021 48 minutes ago, Dom said: So if the ECU is off it connects all injector deives to ground as this is its power-off state? Not really but that is how it will behave. The P&H injector drives have flyback diodes, so if you have 12V on the injectors when the ecu is not powered then 12v will flow through the injector, into the ecu through the diodes and will have a weak ground through some other device that is connected to the same 12V rail. I have modified a rough diagram to show the path below - the circuit is much more complicated but this is just to show the general idea. This "back feed" phenomenon happens with all ecu's which have P&H injector drives. When the ECU is powered up then the 12V rail is live so you have 12V on both sides of the injector so the injector will no longer have current flowing through it. 54 minutes ago, Dom said: The ECU is switched on and all of the 4 injectors are opened constantly. You must have some mistake in the wiring somewhere. I suggest you unplug the ecu and make sure 100% there is 12V on pin A5 with the ignition on. No power on this pin would be the only scenario I can think of that would cause current to flow through the injector when the injector drives are off. Quote Link to comment Share on other sites More sharing options...
Dom Posted June 17, 2021 Author Report Share Posted June 17, 2021 I am really sorry for the late replay, I was really busy. Thanks for the repsonse. working correct now. Wiring was messed up. Quote Link to comment Share on other sites More sharing options...
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