Where to get 12V key on inc cranking for Holley Sniper EFI

A buddy is installing a Holley Sniper EFI on his 70 Charger. The car has the Mopar electronic ignition using a new engine harness that has the electronic harness built right in. The EFI requires 12 volt key on power for the computer. Needs to maintain constant 12 volt power while cranking. My thoughts were to tap into the hot side of the ballast resistor, but we found the voltage at the input of the ballast resistor drops off significantly while cranking. A friend suggested using this ballast resistor point to run a relay for direct battery voltage. Anyone have suggestions? One simple wire is holding us up.

the 12v side of the ballast should be within a tenth of a volt or so of the voltage at the battery + terminal, both referenced to the same ground. If it's not then you have issues, usually dirty or loose connections. A relay will probably band aid the problem but it may show up elsewhere. I've been known to use a relay to feed the ignition all the time anyway. The ignition switch used in out old stuff really was barely enough new, put some age and use on it and it starts showing it's issues.

Hard to do if you're going to keep the ballast resister and the old Mopar distributor. My advice is to ditch the Mopar ignition system and put a Hyperspark distributor on there. Then you can get rid of the ballast resistor and tie IGN 1 and IGN 2 together. Your buddy will thank you later once he understands how much better the Sniper works when it can control timing. Installing a Sniper without timing control is a mistake.

I think you will need 2 relays and tie them together.
I think if you try and use 1 relay you will bridge over the ballast and put 12 volts all the time to the coil.
So you need one from the crank side of the ballast for 12 volts crank to 1 relay.
Then a second from the 12 volt feed to the ballast in run.
Both outputs tie together after the relays to feed the efi computer.

i don't know the exact details of your voltage needs.
when i installed a MSD in my 72 road runner. i just attached both the, i think, lt brown and blue wires together at the ballast resistor. one wire has 12V with key on but goes away when you turn the key start position. the other one has no volts at key on but full voltage when you turn the key start. hook both together and you have power at both key on and key start.
this worked for my MSD, don't know if it will work for you.

MSD doesn't require a ballast, the OP is, I think, keeping the stock ignition which does require a ballast.

Been covered before, for ignition with ballast, place a diode across the ballast.
That’s the way mine’s set-up for 2 yrs with FiTech and Mopar electronic distributor.

Tie the brown and the dark blue together from the old ballast resistor. Blue is hot in run only. Brown is hot in crank only.
Doug

Keeping the stock ignition system, the diode over the ballast terminals would be the correct setup to keep the coil safe in RUN just like it should be with low voltage while allowing full 12 volts when cranking ( from brown to blue wire ) to the EFI being spliced into the Run circuit as must be.

MSD ignition requieres a ballast bypass just on RTR distributors because that's the source for them. MSD ECU modules don't need the ballast bypass because the wire to coil ( with ballast still there ) used for this works just as a remote on signal where the ballast signal is enough to keep it on, not for the source. The load for the module runs in a diff wire.

Need to say, once the diode is set, the ballast wires ( brown end and blue end ) must be connected AALWAYS on that way, being a resistor it doesn't matter which wire is conected on what prong, but with a parallel diode, it must be conected on the correct way. EXCEPT if you link the diode between wires instead at the ballast prongs, which it won't care where you connect the ballast wires just like originally is.

Something on the same here with the OP and not to highjack his thread. I'm thinking of doing the same thing to my car. The only difference is that I have a FBO ECU and it says I don't need the ballast as well. In fact, I'm suppose to use a jumper where the brown and blue is and just stow those two. The FBO ECU needs all juice going to it. My car is a 71 but converted to electronic ignition. I think it will work by doing what BDW said, if I'm understanding correctly. The white box in the picture is what I have

The diaode is another way to do it. but the 2 relay's will isolate the circuits too.
While a diaode might be the "correct" way to do it, if you don't have one the relay's are probably a fast way to get going.

FBO box doesn't need ballast ( per their instructions ) is a diff deal. The diode solution is for the stock ignition which requires/includes ballast on the game

The relay could be an option DEPENDING on the voltage what the relay operates, BUT also requires more wiring involved to make it work. Remember ballast change the operating voltage range with temperature and load going throught so could be switching on and off constantly. Never have made it but just IT COULD happen


The diode is the easier, no need for extra sources/wiring, just jump out both circuits with it... but correctly done, to keep the ign 2 circuit still isolated from the Ign1 while car is in run, which is the deal on this to keep the coil on the ballast operating range, but just jump out the ballast for the ign 1 circuit while cranking

Now, the value for the diode! I can't tell which one could be the best. I'm not in those numbers

voltage should still be 12 volts.
you tap crank voltage off the after ballast circuit. Tap run voltage from before the ballast circuit and you get 12 volts for both. so it "bypasses" the ballast all together for the relay's.

I got what you meant

30- input from blue circuit
87-output to blue circuit
87a ( if 5 pins )-empty
86-trigger from brown circuit
85 ground

but still, a cleaner way just the diode LOL. And if relay gets activated by the low level ballast ouput, could remain activated. Nothing wrong really thought, but maybe switching on and off constantly with Ballast voltage variations. ( just thinking out loud )

Diodes used for solar panel have high current capability (although probably not needed) but more importantly low voltage drop

https://www.ebay.com/itm/382772093682

I appreciate all the input and suggestions. But, I am more confused than when I started.
Is it really this complicated to find a 12 volt power source?
We just need to hook up one wire to make this car run.
There must be dozens, if not hundreds of Mopars with the Sniper EFI or some others EFI systems installed.
Where is everyone hooking up the power wire?

Like I said. Tie the dk blue and brown together. That will provide you with battery voltage running and cranking. Nothing more. nothing less. The ballast purpose was never to protect the coil. It was to protect points or old ECUs. If Your ECU doesn't need a ballast it doesn't need diodes relays or anything else.
Doug

There are multiple places that you could get key on power.
but only 1 for cranking power.

as stated if you need the ballast resistor, you have to do something to tie the cranking power to key on power so the efi computer has power during crank and run.
You do not need to use ballast power for key on if you don't want to.
People generally use those because they are close together when wiring.
most efi setups don't use the original ignition system, so they generally don't need the ballast. Since they take it out, fastest way is to tie those two wires together and viola you power your efi key on and cranking.

I agree with Andy. I originally tried to use the stock dizzy and an old MSD 5C with my setup. After fighting emi for a while, I bought the HyperSpark and and the 6EFI cd box and most of my problems went away. I'm still adjusting the spark and fuel tables, but the car runs so much better.

I already answered your question. If you insist on keeping the old Mopar ignition setup with a ballast resistor then yes, you have to use the diode or the relay approach. But you really should get rid of the old Mopar ignition for the same reason you're getting rid of the carb.

I've rewired many Mopar cars for EFI including both of my own. On my own cars I run IGN1 and IGN2 over to an aux fuse panel and then come off the fuse panel with my pink wires for the distributor, ignition box and ECU. You have to plan ahead when using this approach since you have to decide if you want multiple aux items active during cranking. Typically the Mopar engineers limited the amount of things that were powered on during cranking and I think there is a good reason for that. So when you tie brown and blue together you have to look at the schematic to see what else you might be connecting into the cranking circuit.

That's because there is NOT a single circuit on the ignition system getting full 12 volts on both ign stages ( run and start )

When in RUN, the blue wire ( Ign 1 ) is sourced from ign switch with 12 volts before the ballast, and the wire running to coil gets a reduced voltage rate throught the ballast to protect the coil, just being increased or reduced per ignition needs ( temp, load )

When START ( cranking ) the brown wire coming from ign switch ( Ign 2 ) is the one feeding the coil with a full voltage source bypassing the ballast, however while this wire is still connected to ballast, the RUN circuit keeps energized throught the ballast with a reduced power, but still enough to make the ECU ( which is sourced on a splice BEFORE the ballast ) works.

This also explain why your brake ( and oil if that's the case ) lights on cluster dim out when cranking, since they are sourced from RUN ( ign 1 ) circuit. And FYI these lights in working order or not are also a way to confirm the ballast is good... or not.

Cranking and Run circuits are actually unfused, and the 12 or 14 gauge wires used in these networks ( as long than ign switch itself ) on these stages are plenty for any regular device loads.

The only exceptions on this are the red wire coming into ign switch ( and its internal point ) which feeds not just Ign circuits but also Acc, and heavy loads used on engine bay accesories tipically spliced into the Run circuit like cooling fans and electric water pumps ( gas pumps are not a problem really )

Not that anyone needs me to agree with Andy, but my own experience does. You're really not getting the full benefit of the system you've bought without taking the next steps for ignition control as Andy has suggested. It was critical for me with a boosted application, but even NA I can't see tackling this project and not going the full way.

I understand that they are unfused, that is clear on the schematic. When I hook up an EFI system I run brown and blue to a new fuse panel and then pull the pink wires required to turn on the ECU, distributor and ignition box from that fuse panel. You can argue that it isn't required and that is fine, but it is a very clean way to add a bunch of circuits to the two existing wires. It is simple for someone down the road to see what is going on. The blue and brown wire power the fuse panel and then the three pink wires come off the fuses.

I often also hook up the 12v source and sense wires for a Denso alternator to the same fuse panel. If I do an EFI conversion I usually prefer to update everything to modern parts. Denso alternator, Denso starter, etc. I get rid of the voltage regulator, Mopar ignition box and ballast resistor. I also usually get rid of the factory starter solenoid.

I'm not saying is wrong... to each own for the ppl who understand the system and preffer a custom setup, but just providing the info for the readers on how the stock system works

I guess Mopar didn't hook up the ign system into a fused circuit to prevent a fuse failure by a peak while driving, which could get stalled the engine and, if powered brakes and steering, will make hard to handle and brake. The fuse link protects everything in case of a major failure.

as mentioned, this is just an informative reply

It is not my car. I am trying to help my buddy. That is all. He has the Chrysler electronic ignition with a 440 source distibutor. His choices, not mine.

It needs a ballast. It has the Mopar electronic ignition. Chrysler used ballast resistors on every electronic ignition starting in 1972.

Then you have your answer.

Wel, if you search for info about that you find stuff like this





Not arguing with you but just posting what I find.

Then can you explain why coils used on aftermarket fuel injection, MSD, and current production coils don't fail when they are run without a ballast resistor? A lot of incorrect information can be found on the internet. Many times hard to wade through it all to find fact. My background? 46 years in auto repair as a tech. Currently work at FCA engineering in the Electrical Lab debugging new vehicle prototype electrical issues. Do I know everything? Nope. But been doing this stuff a long time.
Doug

Not all coils are the same.

A coil with a primary Ohm reading of 0.34 Ohm is wound different than a 1.4 Ohm coil. GM coils are about 0.7 Ohm and are required to have a resisror wire inline to the coil's positive lug.

If you run a 0.34 Ohm coil on a stock type ECM, the ECM is being required to switch that higher voltage and amperage and it will burn out the ECM. Yes the ECM always has 12 Volts all the time on the positive side and the Negative is connected directly to the coil. It is the negative side that will burn out in the ECM due to the excessive voltage through the coil. For a stock type ECM you need a total ohm thru the coil at about 1.9 to 2 Ohms (1.4 Ohm coil and a 0.5 Ohm OEM ballast resistor) .

As I said, I'm not arguing with you because I don't have the knowledgement to talk about that with all details, but just sharing what I have found. One of the quotes comes from pepboys website, so we could say is not a "fake" website¿?¿?¿?

And well, I have found coils labeled "no need to run with resistor" or something like that, so everything can be found around points out to the coil deal, including product itself. Maye just because the reason posted by Dave_J ?

I know some ign system like MSD don't make a constant feeding for to the coil. MSD modules handle both leads, so maybe it cuts the power while is not triggering on multisparking allowind to get, somehow" a cooling instant?

Dunno about RTR units thought.

I'm just thinking out loud and trying to learn.

The resistance measurement of the coils makes sense. I stand corrected. So if someone was to chose there old style production coil with a newer style control unit they could have an issue. Or running a new style coil with points or older ECU could be an issue. I still see no need for diodes or relays when running a proper matched set up. Run a coil matched to the ECU being used and follow the recommendations for that system .
Doug

If what you say you do is indeed fact, then you already know the answer to that question, or you damned well ought to.

But to ease your mind they all do the same thing, limit current thru the coil, the ballast resistor is an obvious component external to anything else. Your aftermarket fuel injection, MSD, and current production setups do it internally with current limiting circuits that you cannot see but it is there.