C2 Switched on & crank 12v source

[Jim B.]

1963 SWC EFI CONVERSION - Request any & all recommendations for a 12v switched source (must be 12v during on & crank key positions) to run a Holley Sniper EFI system. This is on a NOM (340) that I have installed with an in-tank fuel pump and am ready to attempt the first start but I need another source than the ignition ballast that I'd initially hoped to use.

If there is a place on the fuse panel that has 12v during run & crank, that would be best I think? Thanks for HELP...

[Richard M.]

Re: C2 Switched on & crank 12v source

Jim,

What is the fuel pump current draw spec?

The Ballast input Pink wire from the IGN switch is 12V during ON and CRANK, but unfused. You could add a fuse(size dependent on question above) to this tap to protect the wiring back to the pump. This would be fine to get you up and running for initial engine tests and break-in.

This Pink circuit(additional Pink wire from the IGN switch, also 12V during ON and CRANK), also goes to the fuse panel as a separate fused circuit to power the gauges, fuel sender and park brake lamp.(Lt Green wires). However there is no "terminal tap" in the fuse panel. The fuse is the top fuse marked GAS GA. You could add a special glass fuse "tap" clip to the outer fuse clip for the power to the EFI. I'd also recommend a separate fuse if tapped from here.

However, for prolonged use, using either method described, I would consider two additional items....

1 - Adding a relay to supply the power to the fuel pump. This would be wired so that the (fused) feed to the relay would come from a battery direct source. The control wire to the relay would come from either above source(Pink circuit). Example of a typical relay for this purpose HERE.

2 - Adding a engine oil pressure monitor switch, from the above 12v relay circuit to power the pump. This would be a safety item to disable the pump if the engine is not in CRANK or RUN mode. With this switch, if you leave the key to ON if engine stops then the fuel pump will be disabled.

This switch could be tee'd into the oil pressure gauge port on the rear of the block with some additional plumbing. Switch example HERE.

Rich

[Jim B.]

Re: C2 Switched on & crank 12v source

Richard, Thank you so much for the suggestion to add a fuse tap to the Gas Ga fuse. I plan to run the pink Sniper wire to that tap and I'll add an inline fuse too if you think that would be safer. There is already a fuse tap on the fuse directly below with a green wire on it but I've yet to figure out where it goes. Everything works on this car including the Vintage Air that may be connected to the green wire. I had been pulling my hair out for a few days before having a very helpful talk yesterday with one of the Holley Instructors who actually teaches Sniper installation. I have been very careful with this first EFI installation (especially with all connections and when supplying 12V power) but the Wizard would never power up and a signal was never sent to the pump either so something is wrong with the electronics in the throttle body. A replacement unit should be here Monday. I received separate wiring diagrams for the Sniper and the in-tank module that has a regulator with the pump so a return line is not needed. Now I understand the additional 12V trigger yellow wire shown on the module diagram is not needed as the Sniper TB electronics supplies that.

Holley support for their parts has been excellent, but I really appreciate you finding an isolated run & crank 12V source for me. Thanks again, jim

[Richard M.]

Re: C2 Switched on & crank 12v source

Jim,

Just to be sure, test the Pink circuit tap at the fuse panel, and the Ballast input(should be top Pink wire) with a voltmeter during ON and CRANK. Stock Ignition switches provide power at the Pink circuit during both conditions, but if the Ign switch you have there is not stock I'm unsure.

To make it easier to access though, I'd think you're better off to use the Ballast input as it's closer to the EFI system wiring in the engine bay. Again, based on current spec of the circuit, especially if powering both EFI AND the fuel pump, you certainly want that fused. Holley may even specify a typical fuse value to use.

The 2nd fuse down from the top of the fuse panel is the ACC feed/Heater(fused). Makes sense if that's what they wired to power the VA system. It is only powered in ON or ACC key mode.

Note that in the panel, all fuse power inputs are the "outer" tap, all fuse outputs are "inner" tap.

e.g. backside of a '67 panel
DSCN4788.jpg

Rich

[Jim B.]

Re: C2 Switched on & crank 12v source

Rich, thanks again, especially for the picture. I initially had the Holley pink wire (that I understand is only a trigger as primary is via 12Ga {+ & -} wires directly to battery) connected to the ballast to test the fuel pump. Although I'm told a shared ignition connection won't damage the Sniper, Holley recommends the pink wire be connected independently to a 12V source to minimize potential RF interference. The NAPA store in the next town has the glass fuse taps so tomorrow I'll get it properly connected. Thanks again for your help as I was hoping to connect to the fuse panel but hadn't thought about using taps to do it and hadn't before checked to find a run & crank 12V point. jim

[Richard M.]

Re: C2 Switched on & crank 12v source

Ok, I see it now it makes sense to not use the ballast per Holley's recommendation.

Just make sure it's fused when you tap off of that "outer" fuse clip position as it is NOT fused there. As you can see on the panel backside photo, the "inner" clip is the fused end. Outer is the heavier gauge Pink from the Ign switch.

Rich

[Jim B.]

Re: C2 Switched on & crank 12v source

For a 3' 16Ga wire, will a 15amp fuse be ok?

[Richard M.]

Re: C2 Switched on & crank 12v source

For a 3' 16Ga wire, will a 15amp fuse be ok?

Yes as long as total draw doesn't exceed that total current spec of both the fuel pump and EFI circuit.

Does Holley recommend a fuse size?

Rich

[Jim B.]

Re: C2 Switched on & crank 12v source

I can't find any specs as it only a trigger for the TB electronics but think the 15A will be fine as the fuel pump and Sniper primary power is directly off a 30A fused wire to the battery. That same harness also has a relay for the pump. Before speaking with the tech rep on Friday, I didn't know the TB had to be powered before the pump would come on. At his advice, I ran a jumper and the pump a few seconds to confirm operation and blow any debris from the line. Pump worked fine so hopefully the Wizard and complete system will also by Tuesday. jim

[Richard M.]

Re: C2 Switched on & crank 12v source

I can't find any specs as it only a trigger for the TB electronics but think the 15A will be fine as the fuel pump and Sniper primary power is directly off a 30A fused wire to the battery. That same harness also has a relay for the pump. Before speaking with the tech rep on Friday, I didn't know the TB had to be powered before the pump would come on. At his advice, I ran a jumper and the pump a few seconds to confirm operation and blow any debris from the line. Pump worked fine so hopefully the Wizard and complete system will also by Tuesday. jim

Ok I thought all of it was to be powered from that Pink circuit. You should be ok then.

Later on you may still want to consider that oil pressure safety switch to kill the pump when engine off.

Rich