highsix_ Posted April 28 Report Share Posted April 28 Have a 1995 sc300 with a 1jz running the plug and play supralink ECU using 2jzgte wiring harness. While tuning the car we ran into fuel delivery issues and changed the fuel pump from a walboro to an AEM unit. No changes as far as the wiring goes. The sc300 already has the 12v bypass mod on the fuel pump ecu so fuel pump is running constantly on key on. After changing to the AEM fuel pump engine continues to run on key off. Hell I can remove the key entirely and the car continues to run. Thought it was ECU hold power at first but after letting the car run for a good minute we figured it wasn't that. You can still rev the motor like it was running normally. Prior to the fuel pump change the car would shut off normally on key off. ECU is still seeing power(even stays connected to laptop on key off.) and fuel pump continues to run. Took voltmeter to main EFI relay to see if it is bad and stuck closed but the relay appears to be good. Tried to disconnect MAC valve to see if it was causing feedback but car still won't shut off. We did spill a ton of fuel into the trunk of the car so I'm not sure if something shorted out that's causing the ECU to still see power. Currently have to pull positive battery terminal off to shut engine down. I will also add that after disconnecting battery ecu does disconnect from laptop and ecu shuts off. Any ideas? Bad ignition switch? Attached is current tune on the ECU. 1jzgtenonvvtisc300lamartune04282024.pclx Quote Link to comment Share on other sites More sharing options...
Adamw Posted April 28 Report Share Posted April 28 2 hours ago, highsix_ said: The sc300 already has the 12v bypass mod on the fuel pump ecu What does this involve? Quote Link to comment Share on other sites More sharing options...
highsix_ Posted April 29 Author Report Share Posted April 29 @Adamw It's a fuel ecu bypass that's commonly done on many sc300's. It essentially cuts out the fuel ecu so that the fuel pump gets 12v constant at ignition/key on and will stay running so long as key/ignition is in on position. The thicker green and black/red 12v wires get cut and joined together like the pictures I attatched. The car runs fine otherwise and prior to changing the fuel pump, engine was shutting down like normal when ignition was switched off. I just tried swapping the main efi relay and still getting the same result. Tried wiggling key in ignition to see if maybe a contact is getting worn and not switching off but I'm starting to think it's not the ignition switch either as the rest of the car electronics (dash, wideband/boost gauges, headlights, etc) all shut-off at key/ignition off like they're supposed to. Quote Link to comment Share on other sites More sharing options...
Adamw Posted April 29 Report Share Posted April 29 Regardless of whether the ecu remains powered up or not, there is an ignition switch signal on pin A1, when this turns off the ecu cuts all spark and injectors. So if it keeps running with ignition switch off then your problem is more around the ignition switch circuit. I dont think the fuel pump should have any relationship to the ignition switch circuit but it is not a chassis I know well. So start investigating why your Ignition switch input is staying alive. highsix_ 1 Quote Link to comment Share on other sites More sharing options...
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