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Posted by: neo914-6 Jul 20 2006, 02:06 AM

What's a good circuit to tap into near the front?

I tried to activate the stock relay and am stumped. I get 12V at #14 in the 14 pin plug on the relay board but no where else.

Where can I find the plug in a '70 chassis, the one pictured near the hell hole did not ohm. It may be cut or maybe another plug.

Are Holley Blue's supposed to be high pitched?



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Posted by: McMark Jul 20 2006, 02:46 AM

Do you still have the relay board?

The FI plug, terminal #3 must be grounded in order for the fuel pump relay to trip. The FI terminal is the four terminal connector near the rear of the relay board. Run a wire from the #3 spade terminal to the relay board ground point and the relay will trip and you will get 12v at the plug.


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Posted by: Nickm1 Jul 20 2006, 07:40 AM

I just run mine off of the ignition wire. So the pump only gets power when the key is turned on. Then to a manual on off toggle switch so if something happens when the car is on i can turn the pump off without killing the power to the rest of the car.

Posted by: neo914-6 Jul 20 2006, 09:52 AM

Thanks Mark, I'll try that. I thought I solved it as it seem all the relays are in series and I only installed one for the pump. When I read the ECU controls it I gave up.

Posted by: BRAVE_HELIOS Nov 11 2010, 06:20 PM

This is probably something out of electrical 101, but is it better to run the positive wire through the toggle switch or the negative wire? Thanks.

Posted by: computers4kids Nov 11 2010, 06:55 PM

I had put a holly blue in the front trunk (75 spot) and quickly removed it...it was just too loud.

Posted by: kg6dxn Nov 11 2010, 07:22 PM

Niether one is better; only different. Typically in a low voltage system (below 100V) the ground is switched, ie. dome light, heater fan, injectors. But this is not always the case, ie. wiper motor, head lamps. If your switch is triggering a relay, the ground is usually switched unless the switch is illuminated. Then the positive is switched. Above 100V, the positive or "hot" wire is ALWAYS switched. In a car it can be both ways. It only depends on your needs.
For my fuel pump I use a positive switch as an override for the EFI computer. This switch is also illuminated but I reverse the to and from leads. This way, if my ECU is running the pump I get feedback to illuminate the switch. If I turn the switch on, I also get a light. My ECU has a positive on/off for the fuel pump relay.

I hope this makes perfect nonsense