AEM ECU Fuel On/Off/Safety Mechanisms | AEM
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Last seen: 2 months 5 days ago
Joined: 11/26/2018 - 01:36
AEM ECU Fuel On/Off/Safety Mechanisms

I am wiring up my AEM Infinity 3 ECU using my car's current (though new) fuel pump. Prior installation did not have an ECU (was old, pre-electronic) so I think the proper route is to have AEM ECU control the fuel pump entirely (and fan as well, and new coils, injectors, etc).


The ECU wants "ignition switch" input .. I suppose this is +12v when the ignition is in the "on" position (and not the "start position"). Thus, I suppose the ECU will then tell the fuel relay to turn on and thus power the fuel pump. 

However, I am not sure what happens when the ignition is in the "start" position. Is the +12v ignition switch still +12v? Does the ECU use the crank sensor input to detect rotation (initially due to the starter motor, then to a running motor) and thus keep the fuel pump going? 


Also, what happens if after running for a while the engine stalls for some reason, then I suppose the ECU has the smarts to turn off the fuel relay even though the ignition switch is still in "on" position.


If I am understanding the above, then I suppose the AEM ECU can control the fuel pump entirely.


Note: I do *not* have fuel pressure sensor connected to the ECU, but I have a manual one for me to keep an eye on things, and also the car does have a fuel pressure accumulator and thus if the pump goes off, it can hold the pressure for a while.


Any input appreciated!



Last seen: 8 hours 14 min ago
Joined: 06/06/2014 - 09:31
All valid statements. The

All valid statements. The fuel pump is powered through a relay and the relay is controlled by the ECU (the ECU outputs a ground to trigger the relay). The ECU primes the fuel pump at ignition switch on and then runs the pump whenever there is a crank signal. If engine stops turning, the ECU turns the fuel pump off. If fitting EFI onto an older car, be aware that many times the 12v on circuit will actually turn off while cranking. Make sure that this doesn't happen otherwise the ECU will turn off while cranking.