MSD Atomic EFI: Tuning Tuning Tuning

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Dr. Marneaus
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

Gotcha looks like MSD has a part to deal with this. I'll have to check and see how low the voltage goes when cranking. Apparently as long as it's about 10.3v it's fine

Is there really no other spot that gets a constant 12v? Nothing ignition wise?
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

FSJ Guy
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by FSJ Guy »

One one Jeep I had that I couldn't find a crank and run power feed, I simply used two relays to combine the two and have power on crank and run. You could probably do it with some big diodes, too, but I had the relays lying around and they worked fine.
Ethan Brady

http://www.bigscaryjeep.com

Jeepless, but I still have a lots of old parts in my garage!
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Dr. Marneaus
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

FSJ Guy wrote:One one Jeep I had that I couldn't find a crank and run power feed, I simply used two relays to combine the two and have power on crank and run. You could probably do it with some big diodes, too, but I had the relays lying around and they worked fine.
Yeah that's basically what the little setup MSD offers is

https://m.summitracing.com/parts/msd-8960

If I'm not mistaken that is basically two relays in one package.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

Flip
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Flip »

Hi,

It's Scott. I knew there was something I was forgetting to tell you on the install.
I used a 3A diode inline to the starter solenoid (STA) on the MSD trigger lead. It's like $2.50 for a big pack of them from Radio Shack (or a good CB shop, if you don't have an RS local anymore :().

Give me some time to wake up and get a cup of coffee. I'll find a schematic for your Jeep, and show you how.
It should just be the trigger lead off the MSD, Power to the MSD should come from a separate lead direct from battery, unless they've changed things, so I need to look at the latest MSD schematic as well. If it still is just a trigger lead, don't use a mechanical relay without a diode across the coil.

Using the diode makes it very clean and easy, Just need to use a stiff piece of nylon wrapped tight to the diode with wires soldered to each end. This keeps the diode from breaking.
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

Hey Scott! Yeah it's just the 'on/off' 12v lead to the MSD power module not the actual power supply.

Any suggestions would be appreciated.

Sounds like you saying to run a diode between the 12v cranking terminal (I terminal on the solenoid) so that it cannot get power going back to it, and then just add another -2v switched power source? I was thinking about how a single relay would work with two power inputs being connected to each other and didn't think about a diode being used to separate the I terminal from the other 12v source.

I'm not a super big electronics guy so bear with me but it sounds like you're saying with a diode I could run one mechanical relay vs using a dual relay setup or the little MSD relay above.
Last edited by Dr. Marneaus on Sun Jun 12, 2016 7:54 am, edited 1 time in total.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by babywag »

One of your DuraSpark box wires should be hot in run & crank. Why not just tap that?
That is the ignition wire source for both of mine.
Single relay, with that wire as trigger on relay.
-Tony
'88 GW (aka Babywag)
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

babywag wrote:One of your DuraSpark box wires should be hot in run & crank. Why not just tap that?
That is the ignition wire source for both of mine.
Single relay, with that wire as trigger on relay.



That's what I was thinking about as well, but haven't looked it up. Nightglide mentioned using one of the prestolite wires as this source for his install however I'm not sure that actually exists in duraspark.

The power leads for the duraspark are a lower voltage switched (that's the red wire which I have going to the s terminal of my solenoid which heads to the + Side of the coil) and a white wire that attaches to the I terminal to get power when cranking, this triggers the spark retard for starting if I am correct. When the I terminal quits delivering 12v during cranking it stops triggering the retard. I don't think this would work for the 12v signal to the MSD unit because it's essentially the same as tapping to the I terminal which is only hot during cranking, and the red wire for the duraspark is only something like 7v when in run because it's the wire that provides the reduced power to the coil.
Last edited by Dr. Marneaus on Sun Jun 12, 2016 8:27 am, edited 2 times in total.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by babywag »

The voltage drop is created by a resistance wire, or a ballast resistor, depending on year etc.

There has to be a wire hanging out somewhere that is 12v crank & run.
I vaguely remember converting my '73 to Duraspark from points, and I know it's there.
-Tony
'88 GW (aka Babywag)
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

babywag wrote:The voltage drop is created by a resistance wire, or a ballast resistor, depending on year etc.

There has to be a wire hanging out somewhere that is 12v crank & run.
I vaguely remember converting my '73 to Duraspark from points, and I know it's there.
Sorry I edited my previous post a bit.

. Did you even need a full 12v for your duraspark conversion? Obviously mind is converted as well from points but the only power connections on the duraspark unit are full 12v at cranking and then the reduced voltage from the solenoid/coil. There is no constant 12v lead heading into it

I believe it would be whatever is in front of the ballast resistor or resistance wire. I'm pretty sure I don't have a ballast resistor. I think whatever wire heads to the coil would be full 12v switched power BEFORE the resistor
Last edited by Dr. Marneaus on Sun Jun 12, 2016 8:32 am, edited 1 time in total.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

Flip
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Flip »

EDIT*************************************
Just realized wire 42 is the I side of the starter solenoid. DO NOT go to that side. Go to the "S" side of the starter solenoid.
My apologies, still waking up from a long night.
Corrected this below in bold
**********************End of edit.

Yep, here is the diagrams for the MSD, I've marked it up with the diode install.
On STA input to the Starter solenoid, there is one lead, the other side has two leads. According to the Jeep diagram I found, this is wire 14. The wire coming off the silver band side of the diode goes to this side of the starter solenoid (attach a ring terminal to the wire end). The other end of the diode gets a wire soldered on, and connected to the MSD "run" trigger (smaller red wire).
So the small red wire from the MSD box is going to go to Run, and also to wire 14 with the diode. The diode is used to keep from feeding back run signal (which would keep the starter motor engaged).

Crap. I don't know how to add the pdf file of the MSD wiring that I added the diode to. Do you know how I can do this? Or can I email it to you?

Here is a picture of the 3A diode. Cathode (silver band) connects to starter solenoid. After soldering on the wires, I just use shoe goo, to glue the whole thing to the nylon stiffener. This is just to keep the diode from breaking due to vibration.
Image

Here is how your starter solenoid should be wired. the post on the solenoid Wire 14 runs to the Key switch S postion.
Image
Last edited by Flip on Sun Jun 12, 2016 8:49 am, edited 3 times in total.

Flip
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Flip »

If it doesn't tell you in the instructions. Don't run the small red wire from the MSD box, to the ignition coil. Keep it away from the coil, back at the firewall or switch. Connecting directly at the coil will induce a high voltage in the MSD trigger wire that will damage it (unless they've added some kind of damper... which I doubt). You can connect to the same wire that goes to the coil, just not directly at the physical coil itself.

Clear as mud?
You are welcome to call me, if it is.
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by babywag »

If you're going to tap the solenoid for power be sure to remove the resistance wire in the harness if it's still there.
-Tony
'88 GW (aka Babywag)

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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Flip »

Dr. Marneaus wrote:Hey Scott! Yeah it's just the 'on/off' 12v lead to the MSD power module not the actual power supply.

Any suggestions would be appreciated.

Sounds like you saying to run a diode between the 12v cranking terminal (I terminal on the solenoid) so that it cannot get power going back to it, and then just add another -2v switched power source? I was thinking about how a single relay would work with two power inputs being connected to each other and didn't think about a diode being used to separate the I terminal from the other 12v source.

I'm not a super big electronics guy so bear with me but it sounds like you're saying with a diode I could run one mechanical relay vs using a dual relay setup or the little MSD relay above.
Sorry, I just saw this post.
You shouldn't need a relay at all. I'm not a fan of relays on a trigger circuit due to tip bounce. Better to use a transistor, but neither are needed on this unit.

Run a diode to the S side of the starter relay. This lead comes direct from key switch Start. Running to the "I" side relies on the solenoid to close. That delays signal to the MSD, and can cause starting issues.
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

But my S Terminal is resisted. It only puts out about 7 volts at run.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

babywag wrote:If you're going to tap the solenoid for power be sure to remove the resistance wire in the harness if it's still there.
But then wont the coil constantly get 12v? I thought it was all set up to only give the coil 7v when running
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.
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babywag
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by babywag »

Dr. Marneaus wrote:
babywag wrote:If you're going to tap the solenoid for power be sure to remove the resistance wire in the harness if it's still there.
But then wont the coil constantly get 12v? I thought it was all set up to only give the coil 7v when running
That's why I said to use the DS crank/run wire, it's before the resistance wire (or should be). Or tap into the wire before the resistance wire.
-Tony
'88 GW (aka Babywag)

Flip
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Flip »

Dr. Marneaus wrote:But my S Terminal is resisted. It only puts out about 7 volts at run.
"S" terminal (Wire 14) should be full 12V during Start. It should drop to almost 0V with key in run, off or Acc position. This is the terminal post on the starter relay that powers the solenoid coil which pulls in the contact tips.

Run (wire 13) should be 12V with key on, at the ignition switch. Resistor (if there is one) should be down stream of the ignition switch.

If your "S" terminal is only at 7V during engine cranking, then there is an issue you need to address first.
It should be B+ to ignition switch, Wire 14 goes to the Neutral safety switch, then from the NSS it goes to the Starter solenoid. Maybe voltage drop through Neutral Safety Switch?

If need be, pick up S and R right at the ignition switch. Wire 14 at the key switch should be full battery voltage during engine cranking. Wire 13 runs to your coil. It should also be full battery voltage at the ignition switch.

So basically you'd make a "Y" with one arm of the "Y" using the diode. That connects to wire 14. The other arm connects to wire 13, and the leg of the "Y" connects to the small red wire from the MSD box.

Just emailed you the modified MSD schematic to match your Wagoneer.
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

Another question that may help me, where the hell IS the resistance wire? Under the hood somewhere in the harness or under the dash?
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.
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Dr. Marneaus
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Dr. Marneaus »

babywag wrote:
Dr. Marneaus wrote:
babywag wrote:If you're going to tap the solenoid for power be sure to remove the resistance wire in the harness if it's still there.
But then wont the coil constantly get 12v? I thought it was all set up to only give the coil 7v when running
That's why I said to use the DS crank/run wire, it's before the resistance wire (or should be). Or tap into the wire before the resistance wire.
The DS run wire is only 7v when running.
Well it ain't just the smoke and the traffic jam that makes me the bitter fool I am But this four-wheel buggy is A-dollaring me to death.
For gas and oils and fluids and grease, And wires and tires and anti freeze....And them accessories, Well honey, that's something else.

Flip
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Re: MSD Atomic EFI: Step 1 - Modifying stock tank for in-tank pump

Post by Flip »

If you get stuck, just call me when you are standing at the Jeep with your volt meter. I can walk you through checking and setting it up.
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