Core ecu lost fuel pump prime signal!

hello everyone, I went to start my car and when I turned the key my fuel pump did not prime... I immediately thought that was odd. when I tried to start the car it just cranked. I checked the fuses they were good also checked the relay and got a strong click when I applied power and ground directly to pins 85 and 86. I swapped the fuel pump and ignition relay and had the same results, the ignition relay clicks when keyed on but fuel pump relay does nothing. I wrote another tune to the ecu and it does not prime the fuel pump after the write is complete like it use to do! When direct power is applied to my fuel pump it does run! I have confirmed there isn't a 12v signal coming from the fuel pump signal wire during the initial pump prime period or when cranking but I can connect to the ecu and see live data with no DTC's recorded. Has anyone had this issue or have any ideas of things to check before i give up on this system?

Have you put a voltmeter to the wire at the ecu to confirm no voltage? Or better yet, an incandescent light bulb to confirm current capacity?

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Originally Posted by gtstorey

Have you put a voltmeter to the wire at the ecu to confirm no voltage? Or better yet, an incandescent light bulb to confirm current capacity?

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hello, yes I used a voltmeter to verify no voltage at the ecu, I also used a simple test light and the wire is dead. I have narrowed it down to connector C pin#3 I think this wire supplies a ground to the fuel pump relay. If I back probe this wire and send it a ground, the fuel pump primes. I'm going to do some more test today and try to get it running.

Is this a first start attempt?

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Originally Posted by gtstorey

Is this a first start attempt?

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no, the vehicle has been running for months now

Does the Core not come with a wiring diagram to tell you whether the fuel pump control is +12v or ground?

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Originally Posted by gtstorey

Does the Core not come with a wiring diagram to tell you whether the fuel pump control is +12v or ground?

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not that i can find. I did find the installation and parameters pdf files which have pinout info, but no wiring diagrams.

Surely it tells you somewhere whether the fuel pump control is +12v or ground. That said, if this ran for months and then stopped and will run with the control wire grounded, then it sounds like it is ground control like I would sort of expect. Have you checked continuity to ground of that pin?

No one knows how reliable these ECUs are yet, so maybe it has failed. I would enter a support ticket.

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Originally Posted by gtstorey

Surely it tells you somewhere whether the fuel pump control is +12v or ground. That said, if this ran for months and then stopped and will run with the control wire grounded, then it sounds like it is ground control like I would sort of expect. Have you checked continuity to ground of that pin?

No one knows how reliable these ECUs are yet, so maybe it has failed. I would enter a support ticket.

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I found that Pin 3 on connector C which triggers pin 86 on the fuel pump relay has a description of 2A low side driver output 9- low side driver control(connect load to switched ignition supply) the loose wire coming out of the harness that goes directly to the fuel pump is grey and has the words fuel pump label on it. I think one of the early youtube videos might specify if its positive signal or ground, but as stated the vehicle has been running since last January. I do not have continuity to ground on the pin that runs to terminal 86 of the fuel pump relay. I did send a support ticket yesterday morning. just waiting to hear back from them. Thank you for all your help. I really appreciate it!

Low side driver would be a ground. Found the pinout online. It looks like you have c3, c3, c8 and c9 all do the same thing. Are any of them grounding?