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Fuel pump relay issue


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So I've just installed Audi TT plug and play ECU in a mk4 golf a few days ago and Im thoroughly impressed and overwhelmed at the same time lol. Everything is working fine except for one small issue.

Everytime I turned the car off the fuel pump relay with start clicking and the fuel pumps will stay on. I can make it stop by turning the ignition back to accessories, wait until the fuel pump stops priming and then turn it off and it will turn off like normal.  I only have this issue with the (link)boost control solenoid wired in, if i disconnect it I dont have the issue. I'm using the factory n75(factory boost control) wiring which matches up with the correct  pins for the ecu. Ive tried switching the wires for the boost solenoid but still have the same issue.

Does anyone have any insight on why the fuel pump relay is acting up when the boost controller is wired in???


Edited by lito
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I dont know how the stock wiring works in that car but from your symptoms it seems that the 12V side of the boost solenoid does not shut off with ignition.  When you turn off ignition the 12V then backfeeds through solenoid into the the aux output and keeps the ECU partially alive.  The only fix will be to power that solenoid from a source that switches on and off with ignition.  A possible reason the problem only surfaced when you swapped valves was that the OEM solenoid was higher resistance so not enough current could backfeed through it.

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