Atomic EFI, inconsistent spark problem

[Bundy]

Hi,

Just bought the MSD distributor and MSD 6A box to finally let the atomic control the timing as it was running without these before. I have all the wiring hooked up correctly, I think. It's a 89'-92' 5.0L 302 with a new-ish painless harness.

The 6A light is on and blinks when cranking. The tach is getting signal as it shows rpms while cranking but it just won't start. I removed the coil plug to the dizzy and had my buddy crank it over to see if the coil is making spark. It doesn't during cranking but as soon as he let's off the key I get a spark but that's it. I'm using the magnetic pickup wires (green/violet) and the white wire from the 6A is not connected.

What am I missing that would make inconsistent spark? The red wire on the 6A box that is responsible for turning the MSD on and off (not the red heavy power lead) is getting constant 12V from #620 circuit (coil) which the painless schematic indicated could be used for an MSD setup as 12V to the 6A. However, when cranking #620 circuit falls to only 8-9V and goes back to 12V when we stop cranking.

So basically I only get spark when we let off the key and the system gets the full 12V, or so it would seem.

I'm stumped. Any thoughts? Should I just run a new wire from the ignition switch to the MSD 6A?

 

[John Marinan]

The old analog MSD 6 boxes hooked up directly to the battery, how does the new box get it's power?

 

[Hozr]

THe voltage of the red "turn on" wires (both atomc and 6a) needs to be MINIMUM of 8.5 while cranking or it won't go. Is there a different circuit that has higher voltage? If not you can use a relay to jump the voltage up.

Maybe test it by jumping the two turn on wires to battery?

 

[pcf_mark]

As noted you need to have 12v key on position and key cranking poistion. To prove you do not have a problem you can run the small red wire to the battery and see if you get sparking.

You can also test fire the MSD with the key off. Take the two wire plug going to the distributor off and temporarily jump the terminals that go to the MSD. Each time you break the connection a spark should jump at the coil.

 

[TAC71]

I had this same issue with an all new system, Atomic, 6A and msd dist. All brand new parts supplied by customer. I have used the Atomic system a number times with no problems before. I was quite happy with the way they install and perform.
Anyway, did the install and it was all good , drove it and it ran fine. After a test run I was checking the valve lash , went to restart and had no spark. Did all the usual checks on a MSD (Major Shitty Device) supply voltage, grounds, blah blah blah and found that the atomic and 6a were not talking. Converted it back to no timing control and it would run but with timing control no luck. Called MSD tech went though it all and they had me send back the atomic for warranty.
Got the new unit and STILL no spark. Again went back to no spark control and it runs fine. Truck is still running on no timing control.

 

[DirtDonk]

...What am I missing that would make inconsistent spark? The red wire on the 6A box that is responsible for turning the MSD on and off (not the red heavy power lead) is getting constant 12V from #620 circuit (coil) which the painless schematic indicated could be used for an MSD setup as 12V to the 6A. However, when cranking #620 circuit falls to only 8-9V and goes back to 12V when we stop cranking.

So basically I only get spark when we let off the key and the system gets the full 12V, or so it would seem.

Something sounds strange. Now realize that I have not read the instructions for the Atomic recently, but do they have you change the way you connect a 6 box from normal?
Reason I ask is that you do NOT put 12v to the coil positive any longer with ANY capacitive-discharge ignition that I'm aware of. Which means you can't use the coil's positive side to feed the control module (MSD-6 in this case) because the module itself powers the coil!

Again, take this with a grain of salt because I could be way off base due to changes in the wiring methods from years ago. Aren't there two separate wires that go to the coil negative and positive from the box now? I forget what color they are (Orange and Green maybe?) just for that purpose?
What color wires come from the Atomic computer to the 6 box?

Anyway, just something to check on. What a CD ignition does, as far as I remember, is feed a very brief, but high voltage spike (about 300volts) to the coil positive, just milliseconds before the Green signal wire tells the coil to spark.
If this is still the case, then your 12v signal with the key on is interfering with the ICM's ability to figure out what's going on.

Of course, this is also a similar symptom to an ignition switch, wire or relay failure as well. So you might have some more diggin' to do.

Sorry if that's off, and I should go re-read the directions before spouting off. But wanted to throw that out there first anyway.

Paul

 

[Hozr]

Another random thought, is your battery dropping voltage during cranking so the entire system drops down? Do you have a jumper pack or spare battery to hook up by chance?

Paul - (I think) He is using the wiring harness coil wire that would normally connect from the ignition switch to coil to power the MSD main power wire. <- which should be fine except it's losing voltage.

 

[Bundy]

Another random thought, is your battery dropping voltage during cranking so the entire system drops down? Do you have a jumper pack or spare battery to hook up by chance?

Paul - (I think) He is using the wiring harness coil wire that would normally connect from the ignition switch to coil to power the MSD main power wire. <- which should be fine except it's losing voltage.

You are correct as the painless harness indicated this was appropriate. I am using the switched 12V that would be used for the coil for the box.

I've tried circumventing the switched circuit and running them straight to the battery but still the same issue. I actually checked the battery while cranking and even the battery drops down to 8-9 volts while cranking so it sounds like the entire setup is not getting enough juice to fire.

I do have another battery I can try but not sure that'll make a difference?

 

[Bundy]

So i hooked up both the ECU and the 6A box to straight 12V... everything was on, still didn't start but I noticed the 6A box was on and then pulsed during cranking but turned off once I stopped cranking. I don't get it. I can unplug the box and plug it back in and the box comes on again but then after cranking it goes off again.

I'll see about jumping the leads on the dizzy to see if I can get a spark out of the box.

Once I figure out WTF the 6A box is doing, Should I run the atomic system through a switched 12V relay?

 

[John Marinan]

I put a switch on the fuel pump line, coming out of the Atomic brain, under the dash. I can cut off the fuel pump when working on anything else that goes through the ignition switch, and it's a very cheap security system. As for the not hearing the pump it may just be up to full pressure. You can look at the handheld controller to see if you have a problem with pump pressure.

 

[Bundy]

That's a good idea John.

I just tested the 6A box according to MSD's instructions and the aforementioned on this thread and got no spark. However, now I am second guessing my test because I got no spark. Seems pretty simple but I laid the screwdriver across the top of the alternator about 1/4-1/2" from the top of the alternator and jumped the magnetic pickup line coming from the box and got jack shit- the alternator should be a good ground, eh? I have all the proper engine/chassis grounds so I'm hoping that was sufficient.

The MSD test says to swap out the coil and see if it works but the coil was fine a week ago. plus I shocked the shit out of myself yesterday when like a genius asked my buddy to crank the engine while I was holding the wire. Seems like an accurate test to me?

So while I'm excited that the box may be my issue I just hope I tested the box correctly.

 

[Hozr]

The alternator? I don't understand this test with the pickup

I'd check spark with a timing light if you have one. See that it's getting all the way to the plugs.

 

[jw0747]

6A MSD box is junk. Send it back. Ask me how I know...

 

[pcf_mark]

Your test sounds pretty solid as long as the alt was grounded which I am sure it is. I assume the coil must be mounted near it so you could test it. I would check your big red and big black wiring to the battery then you may have a bad box. I have only ever seen one that was actually bad. It is usually a wiring or battery issue. I just installed digital 6 MSD and distributor Saturday no problems. I did the test you did to make sure my wiring was good before trying to fire it up.

 

[Bundy]

The alternator? I don't understand this test with the pickup

I'd check spark with a timing light if you have one. See that it's getting all the way to the plugs.

You basically pull the coil wire off the dizzy, pop in a screw driver or a spark tester and put it close enough to a ground and then short out the magnetic pickup line at the 6A box, which should cause it to spark.

Mine did not do this.

Your test sounds pretty solid as long as the alt was grounded which I am sure it is. I assume the coil must be mounted near it so you could test it. I would check your big red and big black wiring to the battery then you may have a bad box. I have only ever seen one that was actually bad. It is usually a wiring or battery issue. I just installed digital 6 MSD and distributor Saturday no problems. I did the test you did to make sure my wiring was good before trying to fire it up.

Mark, none of the wiring is even routed yet- it's literally just sitting on top of the fenders so I can definitely see the power lead and ground are going directly to the battery and are free of obstruction/shorts.

 

[Hozr]

You basically pull the coil wire off the dizzy, pop in a screw driver or a spark tester and put it close enough to a ground and then short out the magnetic pickup line at the 6A box, which should cause it to spark.

Mine did not do this.

Got it, I missed the part with the coil wire. Do you have jumper cables you can connect the second battery with? Not sure why your battery would be dropping down to 8-9 volts during cranking but maybe it needs more juice?

 

[Outlaw Bronco]

So i hooked up both the ECU and the 6A box to straight 12V... everything was on, still didn't start but I noticed the 6A box was on and then pulsed during cranking but turned off once I stopped cranking. I don't get it. I can unplug the box and plug it back in and the box comes on again but then after cranking it goes off again.

I'll see about jumping the leads on the dizzy to see if I can get a spark out of the box.

Once I figure out WTF the 6A box is doing, Should I run the atomic system through a switched 12V relay?

Which wires did you hook up direct to 12v? The heavy constant power wires off of the painless circuit or the smaller 12v switched wires?

If it wasn't the 12v switched wires try connecting both of them with a toggle switch in between directly to the battery. You are just "hot" wiring the system like this and if it fires up just use the toggle to kill it.

This method rules out the MSD stuff if it runs and then you can back trace to the issue. If it's still a no go i would bet the box has gone bad.

 

[Bundy]

Got it, I missed the part with the coil wire. Do you have jumper cables you can connect the second battery with? Not sure why your battery would be dropping down to 8-9 volts during cranking but maybe it needs more juice?

No idea why it drops either but even on the posts of the battery I show this voltage drop.

Which wires did you hook up direct to 12v? The heavy constant power wires off of the painless circuit or the smaller 12v switched wires?

If it wasn't the 12v switched wires try connecting both of them with a toggle switch in between directly to the battery. You are just "hot" wiring the system like this and if it fires up just use the toggle to kill it.

This method rules out the MSD stuff if it runs and then you can back trace to the issue. If it's still a no go i would bet the box has gone bad.

I ran both the atomic ECU and the 6A box directly to the battery, both the power leads and the switched 12V power and after that didn't work is when I tested the 6A box.

 

[Hozr]

No idea why it drops either but even on the posts of the battery I show this voltage drop.

I'd suspect your battery is on the low side of life or it has an internal short. The MSD boxes need full juice

 

[Bundy]

That is what I am thinking too in regards to the short but everything ran fine before I tried installing the 6A. Also if the main power for the painless harness was shorting out I'd think it would have blown the mega fuse...

I'll try swapping out the battery and see if that makes a difference.