Ignition electrical issue. help?

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crj1968

crj1968

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OK I have a MSD 6 AL in my duster with a unilite distibutor. The other day I fired it up and while backing up it died. Tried to restart...nothing.

Looked into the wiring and found what possibly was a shorted wire on the unilite module. Taped things up and got it going again. However, the unilite module looked about 100 years old so I ordered up a replacement to install. Installed it, fired up the car all was good.

Drove the car yesterday and noticed the amp gauge (stock one) was pegged pretty much at any RPM off idle...but it was running fine.

Today I fired up the car and it was idling, it has kind of a lumpy cam so it surges, lights flickering etc. (this I think is key to my issues Ive had much more radical cars and the lights didnt pulse with the idle lope) The amp gauge was following the surges and then like before the car died and wouldn't start again.

I took off the battery cable and put it back on and it instantly fired right back up. ???
 
The charging circuit is fairly independent of the ignition, other than Vreg shares IGN1 power via the key switch. Post a photo of your Vreg and alternator. You didn't bother to tell us the year or engine, and there were electrical mod's made, regardless, so need photos.
 
BillGrissom said:
The charging circuit is fairly independent of the ignition, other than Vreg shares IGN1 power via the key switch. Post a photo of your Vreg and alternator. You didn't bother to tell us the year or engine, and there were electrical mod's made, regardless, so need photos.
Click to expand...

I should also add that when it doesnt start, it does crank...

70's LA 318 motor. Stock alternator. Standard 2 pin voltage regulator mounted on firewall. MSD wired correctly with ballast resitor. Ive driven the car a lot just like it is, but this pulsing amp gauge thing has just popped up

The only thing I can think is the MSD box has some sort of reset and doesnt like the pulsing current and shuts down...then removing a battery cable resets it.

I'd guess the alt or regulator is acting up...
 
Sounds like: 1) the voltage regulator has failed so as to command full alternator output; 2) there is a shorted brush in the alternator; 3) there is short on the field wire from the alternator to the VR, causing full field current; 4) there is a poor ground. Any of these would case full balls-out charging out of the alternator; that would explain the full charge deflection on the ammeter. Put the voltmeter across the battery and start the car. If the voltage goes above 14.4 or 14.5 V or so, and heads up to towards 15 volts or more as you raise the ilde RPM"s, then this is the case. The MSD is rated to work off of 18V but who knows what spikes the systems is seeing.

If you don't see this high voltage , then I would be thinking of a short in the main output of the alternator, that would cause the full ammeter deflection; that would be a serious situation. Because of this, don't be cruising around 'til you fix this.
 
Do you have an ammeter / voltmeter? What is it doing?

I don't know much about the Unilite / MSD stuff. I guess I'd suggest you charge the battery up so that's not an issue, disconnect an alternator field and troubleshoot and fix the ignition and get it running good.

Then attack the charging issue.

It might be possible that overcharging (if that is the trouble) is causing the ignition symptoms
 
I ran a ground wire to the regulator casing no change. Changed the regulator for the helluvit since I had one lying around same thing.

14.7 v at battery with car idling.

The MSD deal has been on the car for a long time and it was running like a top. I dont much abou them either but they are easy to test and it's good to go.

Looks like an alternator issue. Will try your method with a clip wire next....trying to sneak out and work on it between everything else begging for my attention around here. Thanks guys.....
 
You should check at a good fast idle, or simulated "low cruise."

EG if the engine is idling slow, the alternator is "just starting to" put out

So if say, the field is grounded, causing "full charge," and the battery is a bit down, you could misinterpret an idle reading for "normal."

But if you speed it up and the voltage climbs up towards 15, you know you have a problem in the field / regulator

The "usual suspects"

Voltage drop in the ignition harness feeding the regulator. That is, low voltage TO the regulator causes OVER voltage at the alternator output

Voltage drop in the ground circuit, IE VR not grounded to battery NEG

Sometimes, battery problems

The mentioned guess, IE grounded green brush causes "full charge" at the alternator

Bad VR, but actually, this is fairly rare.
 
OK thanks for the info- yeah I went out and sped it up and batt voltage steady at 14.4 Amp gauge wasn't pegging anymore off idle. ? Right about center gauge but shaking a bit. Seems what ever it is has changed for the better a bit without me making any real changes.
But I did push on the firewall plug...maybe your voltage drop at ignition harness is it...

I'll check it out
 
Well 14.4 is certainly OK, though not considered "perfect."

The shaking gauge may be a loose connection

Try this........in subdued light or darkness, run the engine and rev it while looking inside the alternator. Look for a "light show" of electrical arcs between the stator windings. Be careful not to confuse this with sparks from the brushes, which are normal

The number one suspects are poor connections in the bulkhead connector, at the ammeter and in the ammeter itself.

Less "popular" is a bad connection at the eyelet terminal at the alternator, and very rare is a failure of the welded splice. This is a factory splice in the black ammeter wire up under the dash. You have to untape the harness starting at the black ammeter terminal for a few inches to find and inspect it.
 
one other thing to check... make sure none of the battery cables/wires going to the starter / starter solenoid have any bare spots / rubbing on anything. use one of these on the battery posts/terminals:
images

also if there is a short inside the starter solenoid it will get you.
make sure the starter cables are not shorting. that fat cable going to the starter is always on.
 
Just a quick update and thanks to everyone for your help.

I eliminated the bulkhead connectors. And still had the issue. then I eliminated the AMP guage and the flickering lights stopped - something was up with the gauge apparently.


Thanks!
 
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