Ignition switchable fuse box..... - Team Camaro Tech
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post #1 of 11 (permalink) Old Sep 25th, 14, 10:42 PM Thread Starter
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Ignition switchable fuse box.....

I have a 4 fuse box next to my painless wiring main box, and the 4 fuse box is connected to the ignition. I pulled each fuse and tested each socket, 3 were getting 11.5 volts, one was getting 2.5 volts. I haven't pulled it yet to see what is connected to that socket, but if my MSD digital 6 plus ign switch wire is connected to that, is that enough to prevent the box from working at all?

Like I said, I don't know yet if that is where the wires go(just knowbiy goes to that 4 fuse box). Its going to be a pain to unmount so I'm calling it a night, do it tomorrow. Secondly, What would cause that, a frayed wire?

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ
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post #2 of 11 (permalink) Old Sep 26th, 14, 03:49 AM
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Re: Ignition switchable fuse box.....

MSD boxes require full power to turn on.
This turn-ON power is not a current demanding, maybe half an ampere, but full battery voltage is needed in triggering the box on.

Seems the construction of the fuse box, the supply side would be a buss bar and power should be the same on one side of all fuse sockets.
On the other side of the sockets, there may or may not be voltage there depending upon load connected.
In case of the MSD box, there may be some feedback from the box and this may be the value read.
When fuse box is removed, it will be interesting to see the construction.

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post #3 of 11 (permalink) Old Sep 26th, 14, 06:10 AM
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Re: Ignition switchable fuse box.....

I recommend feeding the MSD directly from the battery which can be relied upon to limit and voltage fluctuations (the transistors in the MSD box hate low or high voltage; and it can destroy the box if it experiences either condition). You turn the box on and off by way of a delay (solenoid) activated by the ignition switch.

The stock wiring is undersized to feed even the stock 36 AMP circuitry the Chevy engineered for your Camaro back in the sixties. Basically everything runs off of the battery, and the alternator is on the car just to recharge the battery. This is why your lights are dim at idle and brighten only when the motor spins above 2500 RPM. Adding heavy loads (such as a modern sound system, electric fuel pump, or even a MSD ignition box), can easily overwhelm the stock wiring (Painless Wiring does offer heavier gage wires than stock or AAM's stock replacement wiring). Copper wiring that isn't heavy enough to carry the amperage becomes a resister dropping the voltage.



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post #4 of 11 (permalink) Old Sep 26th, 14, 09:48 AM
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Re: Ignition switchable fuse box.....

Is it possible that that particular fuse is powered by the original ignition wire to the coil? That would be a resistance wire designed to only supply the 6 volts to keep the original points from burning out prematurely. Im not familiar with that fuse box setup but if that fuse is designated as the one to use for ignition, it might be powered by the resistance wire circuit.
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post #5 of 11 (permalink) Old Sep 26th, 14, 10:23 AM
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Re: Ignition switchable fuse box.....

In the MSD instructions it tells you to connect the heavy 12 gauge red wire to the + side of the battery or a positive battery junction such as the starter solenoid. Connect the heavy 12 gauge black wire to the negative side of the battery or to engine block. The small red wire is responsible for turning the MSD On and Off. Connects to a switched 12 volt source such as the ignition key or switch.
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post #6 of 11 (permalink) Old Sep 26th, 14, 10:46 AM Thread Starter
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Re: Ignition switchable fuse box.....

Quote:
Originally Posted by Cdminter55 View Post
In the MSD instructions it tells you to connect the heavy 12 gauge red wire to the + side of the battery or a positive battery junction such as the starter solenoid. Connect the heavy 12 gauge black wire to the negative side of the battery or to engine block. The small red wire is responsible for turning the MSD On and Off. Connects to a switched 12 volt source such as the ignition key or switch.
Yes. That is The wire(ignition wire) I was talking about. It goes to the 4 fuse box, which is connected to the ignition. I'll know when I get a chance to remove the box if it is the one only getting less than 3v.


For reference, mine is wired like the bottom diagram on page 11 of the box (6520) manual. Coil wires and magnetic pickup all look good, still examing power and ignition wires, later today. Just ran out of steam last night.

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ
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post #7 of 11 (permalink) Old Sep 26th, 14, 12:23 PM Thread Starter
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Re: Ignition switchable fuse box.....

I found a relay on the other wide of the 4 fuse ignition fuse box. I pulled the relay, put it back, loosedbthe fuse box, and now the Digital 6 plus LED light is lit up with the ignition in the on position, and blinks during cranking.

I tried to start and it tired to fire up (run)VERY briefly by by, but nothing since, just cranking again.

So the 6+ is getting power now. I pulled a plug out and set it on the valve cover and started cranking in the dark, couldn't see a spark. I did the test they suggest in the instructions, to unplug the coil wire from the distributor, set it 1/2" from a ground, and short the magnetic pickup wires. Still didn't see a spark.

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ
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post #8 of 11 (permalink) Old Sep 26th, 14, 01:21 PM Thread Starter
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Re: Ignition switchable fuse box.....

Tried it with several in plugs, even recorded one at 60 frames per second while cranking to make sure.

I out my voltmeter on the power wires that go to the coil(orange and black).

When cranking, with the voltmeter set to the 9V battery setting, it was reading .16-.25 on the orange and black wires.

(When I had it on VDC or VAC it read zero, why I put it on battery).

So the coil isn't getting more that .25 V from the 6+?

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ

Last edited by SnakeEyes; Sep 26th, 14 at 01:38 PM.
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post #9 of 11 (permalink) Old Sep 26th, 14, 03:49 PM Thread Starter
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Re: Ignition switchable fuse box.....

Okay, this is weird....

That fuse that only gets 3v now suddenly gets 8v, is the main power wire for the 6+.

Here is the thing, the relay I mentioned? The ignition and the main power wire both run to it.(yeah, the guy who installed it obviously didn't read the instructions)

The power wire goes from the 6+ to the 4 fuse box, then to the relay, and then finally ends in the accessory port at the main fuse box.

The Acc port the heavy wire uses at the main box gets 12v. The fuse port the heavy wire uses at the 4 fuse box gets 8 volt.

The only thing in between is the relay. I checked the heavy guage wire on the relay port and it reads 12v

I'm guessing the bad relay can cause the voltage problem?

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ
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post #10 of 11 (permalink) Old Sep 26th, 14, 04:10 PM Thread Starter
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Re: Ignition switchable fuse box.....

I got it started.

I did NOTHING but test circuits. The one that was getting 3, then 8, started getting 11, so I tried to crank and saw spark, put the coil wire on and it started up quick.


Talk about a "wild goose chase", only to have the goose cooked and on the dinner table after it got away and I went home.

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ
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post #11 of 11 (permalink) Old Sep 26th, 14, 04:52 PM Thread Starter
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Re: Ignition switchable fuse box.....

Final update:

The main power wire barely fits into the socket, I'll need to trim some of the plastic off the fitting. I'm wondering if it was the issue, unstable connection giving random voltage readings.

Make senses, but why start causing a problem now? Probably because I am hiding the wires better now and there is less slack, it gets loose easily. Either that or there is a break in the relay wiring.

Either way, if it happens again and the wire isn't loose, I know what wires to tackle.

Thanks for the input, everyone.

Formers: 1969 RS 350, 700HP 1967 Flash-in-a-pan Firebird 400, 2002 Z28 M6 1SC/1SZ
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