Engine bay, switched 12V

[71GTX440]

I am installing the Holley Sniper 1 EFI onto my 408 Stroker.
Made a bone headed mistake and failed to isolate a switched 12V source prior to removing carb and fuel lines.

Any solid facts on which wire under the hood is a 12V switched source?

 

[rmchrgr]

NOTHING. There are no reliable switched 12V sources under the hood if everything is mostly stock electrically. There really is no easily accessible switched 12v source on any muscle-era Chrysler product.

What ignition are you using? If you're not using the Hyperspark there's little point in using the Sniper since you can't control timing. If you have the Holley or even an MSD type ignition then you have to tie the IGN 1 and IGN 2 circuits together which can be done by gutting the ballast resistor and installing a jumper wire between the two points. That creates a switched 12v source under the hood but you can't do that if you're still using an OE-type ignition system.

Is it a Sniper 2? Did you get the power distribution module? That box will definitely make your life easier. *************************

I installed a Sniper on my '68 Coronet several years ago but I rewired the entire car beforehand and created a 12v buss off the switched ignition feed in the fuse box. I wouldn't attempt anything like that with an original fuse box either...

Do this right or you will have problems, guaranteed.

 

[gkent]

Run your wire through the firewall to the ignition switch.

 

[gkent]

Join the Holley Sniper owners and tech Facebook page. You'll get more accurate and informative answers there. Some responders can be ******** but you'll figure out who those trolls are quick enough.

 

[rmchrgr]

Join the Holley Sniper owners and tech Facebook page. You'll get more accurate and informative answers there. Some responders can be ******** but you'll figure out who those trolls are quick enough.

Actually, Holley has several EFI forums.

Holley Sniper Forum

I had a thread a few years ago here where I documented a lot of what it took to convert my old '68 Coronet to EFI.

'68 Coronet EFI/4 speed

 

[71GTX440]

NOTHING. There are no reliable switched 12V sources under the hood if everything is mostly stock electrically. There really is no easily accessible switched 12v source on any muscle-era Chrysler product.

What ignition are you using? If you're not using the Hyperspark there's little point in using the Sniper since you can't control timing. If you have the Holley or even an MSD type ignition then you have to tie the IGN 1 and IGN 2 circuits together which can be done by gutting the ballast resistor and installing a jumper wire between the two points. That creates a switched 12v source under the hood but you can't do that if you're still using an OE-type ignition system.

Is it a Sniper 2? Did you get the power distribution module? That box will definitely make your life easier. I have a brand new one I will sell if you're interested.

I installed a Sniper on my '68 Coronet several years ago but I rewired the entire car beforehand and created a 12v buss off the switched ignition feed in the fuse box. I wouldn't attempt anything like that with an original fuse box either...

Do this right or you will have problems, guaranteed.

As stated, it's the sniper 1. Ballast is already gutted and I epoxed the jumper wire so it looks stock.
I am running the MSD 6 AL with everything wired in. Been driving it for over two years with zero issues. Tired of the hard cold starts and constant start, restart, restart if I don't drive every week.

Thinking of pulling switched 12v from under dash and running to the engine bay.

 

[71GTX440]

Run your wire through the firewall to the ignition switch.

This is the solution I was thinking of doing. Have to get in the schematics and isolate which wire would be correct. Thinking perhaps the 3-prong pigtail under the dash or maybe the radio harness as I don't have a radio

 

[71GTX440]

Join the Holley Sniper owners and tech Facebook page. You'll get more accurate and informative answers there. Some responders can be ******** but you'll figure out who those trolls are quick enough.

I am a member already, not a lot of info on the 71-74 b bodies on there

 

[gkent]

There should be an empty slot in one of the bulkhead connectors - run the wire through there.

 

[rmchrgr]

As stated, it's the sniper 1. Ballast is already gutted and I epoxed the jumper wire so it looks stock.
I am running the MSD 6 AL with everything wired in. Been driving it for over two years with zero issues. Tired of the hard cold starts and constant start, restart, restart if I don't drive every week.

Thinking of pulling switched 12v from under dash and running to the engine bay.

All that red wire does is turn the ECU on - I doubt that's what is causing your hard starting issues since it does not have anything to do with the tuning aspect of the system. By gutting the B.R., you essentially have IGN 1 and 2 tied together already and have a switched 12v source. You'd have to do that with any MSD type ignition or it wouldn't run at all. If the Sniper turns on and the engine cranks and eventually stays running then wherever you have that wire already should be OK. Are the main ECU power and ground wired directly to the battery? Holley kind of beats that into you so hopefully you at least did that.

I think it bears repeating that there's almost no point in running EFI if you can't control the timing. An MSD is fine but it's not possible to control the timing without the Hyperspark ignition box and distributor. I believe that your startup issues would be solved or at least dealt with more efficiently if you had the ability to adjust and control the timing beyond what's in the distributor.

We have to presume you don't tune with a laptop either because if you did you'd know there are specific startup parameters in the software. Having a startup data log would go a long way to helping determine any specific issues. The Holley forums allow you to upload data logs so people can view it and offer help. Plus, learning how to build custom ignition and fuel tables in the program will also give you a good idea of how the whole thing works. EFI is not a magic bullet, you have to put some effort into it.

Anyway, the link below is to a page that details how to tune your startup. It sort of presumes you are using a laptop and are familiar with the Holley software though so just be aware of that. I personally wouldn't want to try doing this type of thing with the little hand-held screen as it's very limited in what it can do.

Startup tuning

 

[451Mopar]

If you tied both sides of the ballast resistor together, it should be OK for the pink "key power" wire if the ignition switch is good.
The large power wire goes to the battery.
This has worked on the cars I have done that use aftermarket ignitions where the ignition coil does not need a ballast resistor.
If ignition coil needs ballast resistor, the pink wire could be connected to each side of the ballast through diodes. Adding a capacitor to the pink wire (isolated by the diodes) might help cover up short intermittent power drops when switching key from start to run?

 

[91r/t]

Could we just run the pink wire to the battery as well with a switch to it to toggle on before/when you also turn the ignition key on? It would double as a kill switch for the car. I would think the amperage draw would be small on that circuit as it is just the trigger wire for the Holley ECU correct? Heavy duty toggle switch under the dash going from the battery through the switch to the unit with a fuse inline and done. Correct me if I am wrong.

 

[Some Car Guy]

How many amps does this need? Could you run it off the gutted ballast? I’ve seen a piggy back spade that slips on a male end and gives you two spades to use. That would give you a clean install.

 

[gkent]

There's a very good reason they want it hooked to a keyed source !!!

 

[91r/t]

There's a very good reason they want it hooked to a keyed source !!!

So it doesn't get forgotten about and left on? It would be the same as if you were hooking it up on a drag car and turned the main power switch on and it went live I'd think.

 

[gkent]

In any race car you'd be inclined to hit the main power switch. Not so much in a street car with a key! Put a little extra effort into doing it right and you'll never wake up to a car fire or an overheated and blown ecu.

FWIW, the Holley Terminator ECU is hooked direct to the battery but the red/white wire is to keyed power. If they'd wanted it hot all the time they would have made it that way.

 

[91r/t]

Just thinking outside the box is all. I run the stock ignition, so if I want to do it “right” I will have to grab power from both the brown crank and blue run power wires and send them both to the pink wire on the ECU trigger wire. Also wasn’t sure if it would surge the ECU when the power cuts from keyed to crank back to keyed.

 

[gkent]

Hmmm. For the sake of simplicity the key has two positions, RUN and START. in the START mode both the ignition AND the starter are getting power. In RUN mode the starter is out of the loop. But your problem is the fraction of time from the START to RUN position. You can't just use a simple jumper between the two or the starter will continue to be engaged.

Here's how you do it:

You make a jumper to go between the RUN and START terminals BUT the START section has a diode to stop the current flow to that terminal when the key is in the RUN position - thus preventing the starter from continuing to be engaged.

As per this crude diagram, black is the jumper, red is the current flow.. The diode shows the direction of current travel. In the RUN position the diode blocks the current from engaging the START circuit. In the START position the current can flow to the RUN circuit but it does that anyway.

 

[451Mopar]

Hmmm. For the sake of simplicity the key has two positions, RUN and START. in the START mode both the ignition AND the starter are getting power. In RUN mode the starter is out of the loop. But your problem is the fraction of time from the START to RUN position. You can't just use a simple jumper between the two or the starter will continue to be engaged.

Here's how you do it:

You make a jumper to go between the RUN and START terminals BUT the START section has a diode to stop the current flow to that terminal when the key is in the RUN position - thus preventing the starter from continuing to be engaged.

As per this crude diagram, black is the jumper, red is the current flow.. The diode shows the direction of current travel. In the RUN position the diode blocks the current from engaging the START circuit. In the START position the current can flow to the RUN circuit but it does that anyway.

View attachment 1760946

Good info, but depends on the ignition switch. I know on my 1969 Coronet the ignition switch has different contacts in the "start" position for the starter and ignition system, so connecting both the ignition start and run wires works without triggering the starter (via the relay.)
I mentioned using diodes on both run and start to the low draw EFI power wire with a filter capacitor. I don't think the EFI power wire draws much current, but if a higher current is needed, the same idea could be used to trigger a relay.
When it comes to wiring problems, quality parts and workmanship matter just as much as having the schematic correct.