Keyed Power for EFI?

[MKSpeedlab]

I was wondering if anyone knows, or maybe they have installed an EFI system in their car, which wire under the hood would work for a keyed power that also stays on when starting. I have tried to look through some wiring diagrams but just gave myself a headache. I was hoping that the throttle position solenoid wire would fit the bit but was having a hard time testing. The car is a 72 although Im guessing there werent too many wiring changes over the years. 

 

[midlife]

Look for red/yellow wires on the engine gauge feed harness (outboard most female bullet on the 4 pin plug on the headlight harness). 

 

[MKSpeedlab]

Sounds good, I will take a look tomorrow and see what I can find. Im guessing drivers side somewhere near the washer tank? Do you know if the throttle position solenoid would also work since its no longer on the car? I was looking at the wiring diagram and its a red wire with yellow stripes so is that the one your talking about? Its located on the drivers side of the intake manifold. 

 

[midlife]

That wire is the throttle position solenoid.

 

[TheRktmn]

Depending on the solenoid it is hot during run or when the A/C is on, but not during start.

The wire midlife directed you to meets both requirements. 

You can also tap off the I post of the starter solenoid (same circuit, same function, different place).

 

[MKSpeedlab]

Ok, I'll have to see if I can find where the wire he mentioned is located. 

 

[midlife]

Depending on the solenoid it is hot during run or when the A/C is on, but not during start.

The wire midlife directed you to meets both requirements. 

You can also tap off the I post of the starter solenoid (same circuit, same function, different place).

No, the I post would have only 9 Volts or so due to the resistor wire during the time the key is in RUN position. 

Another wire is the green/red wire going to the voltage regulator, but only if you have an ammeter in the dash cluster.

 

[MKSpeedlab]

No, the I post would have only 9 Volts or so due to the resistor wire during the time the key is in RUN position. 

Another wire is the green/red wire going to the voltage regulator, but only if you have an ammeter in the dash cluster.

Oooo that might work nice, I the car does have the factory ammeter. Although it will likely change the ammeter to a voltmeter at some point. I will check for that wire first. 

 

[TheRktmn]

No, the I post would have only 9 Volts or so due to the resistor wire during the time the key is in RUN position. 

Another wire is the green/red wire going to the voltage regulator, but only if you have an ammeter in the dash cluster.

I stand corrected.  I was thinking of activating a relay or soft switch like the MSD box, not  a constant power source.

 

[MKSpeedlab]

That said, I likely will hook it to a relay to make sure the EFI is getting a nice clean 12v when the key comes on. I have heard that the EFI systems like things to be as clean as possible without any noise. 

 

[MKSpeedlab]

The green/red wire for the voltage regulator worked perfect. Note to self, dont buy relays off Amazon anymore. But after replacing the relay I was using with a quality one its working great.