MSD 6AL debug / Correct alternator connections

[elevenssc]

Car runs very rough at idle, almost like it's missing.  There is a very heavy odor of fuel like it may be missing.  It almost seems like the MSD is in rev limiter mode.  I had a 6000 rpm chip in the box, and swapped it out with another and no change.    I replaced plugs and no change.   

I'm only getting 11.5V out of the alternator at idle.  I'm remembering that the MSD's need 12-14 volts to work propperly.  Is this correct? 

I obviously dont have the alternator wiring hooked up correctly either.  I've got the batery power to the threaded post (toward the fender), and the "alt excitor" wire it one of the spade connectors (on "top").  I'm feeding the volt meter off the other spade connector (toward engine). 

Something is not right...any help would be appreciated...

[brads70]

I had a needle and seat for the float level go bad once ( Holley) and had fuel pouring out the vent tubes. It ran a little rough and smelled like raw gas. If you have a Holley check you float level?

[Chryco Psycho]

solve the charging issue first & get the power up to 13+ v then see if the problem continues

[elevenssc]

Looking at the wiring diagram, and doing some on-line research, does one of the field spade connectors need to be grounded to get the alternator to work?  If so, does it matter which one?

In the 1970 Barracuda wiring diagram, one of the field spade connectors went directly to the "FLD" terminal on the voltage regulator, (The voltage regulator was grounded).  The other field spade connector tied into the wire from the "IGN" post on the regulator.  Since I'm using an MSD, I'm thinking all I need to do is to ground one if the FLD terminals, and use my "Alt Excitor" wire from the new harness on the other spade.  The volt gauge then gets fed off the threaded terminal.

Any thoughts???

[UKcuda]

11.5 v at a slow idle is OK as long as it rises as soon as it comes off idle. 

The MSD should be OK to run at 11.5 v at idle.  You should be measuring the voltage between the threaded post and ground, not from a field connector.

The MSD does not allow you to dispense with the regulator.  You need to keep it the way you describe in the 1970 diagram.

For Mopar alternators with two field terminals you should have 12v to one of them and the other one goes to the regulator (it doesn't matter which way round they are because it is making AC).  The regulator switches the connection to ground until the system voltage rises to the correct level and then switches it off again (above idle it is switching very rapidly).

If you ground the alternator field connector (ie. by-pass the regulator) the alternator windings will go full field and produce a high voltage.

I wonder if you have got confused on the internet looking at the wiring schematic for the earlier alternators?  On the early Mopar alternators (pre E-body) there is only one field connector.  The other end of the winding is grounded internally, but that is because the regulator on those systems sits in the 12v supply to the field connector and switches that instead of switching the ground side.

The comment above about checking your float level and inlet needle sounds a more likely source of the bad idle and fuel smell.  It's probably not being caused by the charging system because the engine should idle fine even without an alternator fitted at all ('til the battery goes flat).

[elevenssc]

Thanks UKcuda,

I have 12V to one of the field termiinals on the alternator.  Sounds like I need to get the voltage regulator back in the circuit and connect the other field terminal to the voltage regulator.  Does the regulator care which terminal I use on it? (IGN or FLD)  I would assume FLD, but I've assumed wrong before.

I want to get this right.  Getting the smoke back into the wires once it is out is a pain

[UKcuda]

No problem,  you do need to connect the regulator the right way round; you need 12v to the IGN and the FLD goes to the alternator field connector.

In fact the regulator IGN connection is on the same wire as the 12v that goes to the other field connector on the alternator, so in practice you can think of it as having two wires running from the regulator connectors to the alternator field connectors and then connecting a 12v feed from the ignition switch to the wire that goes to the IGN connector on the regulator.  The regulator must also have a good ground.

What is happening is you are feeding +ve system voltage to the regulator and also to one side of the alternator field windings.  The regulator watches the +ve signal on the IGN terminal and if it drops below 13-14v it switches the other side of the field windings (FLD) to ground.  That completes the field circuit and the alternator starts hitting the battery with some charge.  That in turn makes the system voltage go up.  The regulator (which is still watching the voltage on the IGN connection) sees the system voltage increase and disconnects the FLD from ground.  The system voltage then drops back and then it all happens again.  In practice it is cycling so fast it gives the impression of a smooth output.

[elevenssc]

Thanks UKcuda...this is exactly what I was looking for

I'll get it connected per your instructions and let you know how things go...

[elevenssc]

Hooked things up per UKcuda's instruction and the alternator is now charging!  Thanks UKcuda!!!

I am noticing that as the RPM's increase, so does the voltage.  Only went up to 2500-3000.  Is this normal?

Still have the rough idle/fuel smell.  Looks like a carb issue now.  This I can handle 

[UKcuda]

I am noticing that as the RPM's increase, so does the voltage.  Only went up to 2500-3000.  Is this normal?

It would usually go up as you come off idle but it should not just keep going up and up.  It should stop somewhere in the 14s.  How high does it go ?

[elevenssc]

I'll get the carb issue figured out first and let you know how high the voltage goes...

[elevenssc]

Well...the carb was the culprit...needle and seat were sticking, though there was nothing obvious.  Had to take it apart twice before it behaved

Now that it dosent flood at idle, it still runs rough.  Only getting 12-15 inHg at idle.  I'm suspecting the plug wires may not be up to snuff with the new MSD   Gonna replace 'em anyway.  They are about 15 to 20 years old, so a new set cant hurt.

I left the batery charger on the batery while checking vac at idle and noticed that the volt meter is not reading anything.  Checked the alternator and nothing there either (at least the gauge is reading correct  .  So the question is...did I fry the alternator (or voltage regulator) by leaving the batery charger on while the the car was idling?  I dont think so...but I'll take the alternator in to get it checked.

Another question...do Optima Red Top bateries follow the same 5-7 year life window as standard bateries?  I'm thinking mine is on the outs too...

(guess the MSD is finding all the weak electrical links  )

[Chryco Psycho]

I have not seen any damage done having a battery charger on the car while it is running , there is just less load on the alt that way
 Optima batteries can fail very quickly if they are not used much , on the other hand the last one I bought lasted 13 + years

[elevenssc]

The latest installment in the ongoing saga.  The two issues I've been wrestling are still present...insufficient alternator charging and rough idle/running.

First the alternator charging issue.  To keep this short, alternator passed test at the local parts store, volt gauge reads correctly, getting batery voltage to the FLD terminal at "run", everything is grounded correctly, all wire connections are sound, installed a new voltage regulator and I'm only getting 10.5 V at the gauge at idle.  The batery voltage was a little over 11V...What gives?   I dont have the balast resistor in the system, do I need it with the MSD and "original" alternator?  If so, how does it get wired in?

The rough idle/running has me puzzled too.  New plugs, wires, dist cap, rotor, MSD coil and 6AL.  It's running like it's missing.  Checked each cylinder at idle with the timing light and each one is firing.  Every once in a while it "pops" like a backfire when held at about 2000 rpm for a while.  Took the car out for a little shake down and under a mild/hard accell, it sounded like all 8 cylinders were knocking.  Would no vac advance cause this?  Could the charging problem be related to this? (I've been treating them as separate, but maybe they are related???)

One other thing worth mentioning (after racking my brain about everything that could be the cause),  When installing the engine and tranny back in the car, the hoist chain was resting on the distributor base.  Not sure how much pressure was on it, but I did have the whole assy angled pretty good to get the engine/trans into the hole again.  Could I have messed up the distributor base to cause the rough idle/running?

Oh the joys of customizing our rides...I think I need a beer...

[elevenssc]

I think I figured out half the problem.  I got to thinking about the distributor and checked the timing.  I reset the timing to 5deg BTDC and things seemed to smooth out.  It still dosent feel right, and a light bulb went off.  I did replace the harmonic balancer and what I'm feeling feels like the balancer is not correct.  I still have the original balancer, and will swap it out to see if that resolves the issue.  I remember posting a question about the internal/external balancer at the time and remember thinking I got the correct balancer.  Guess I'll have to re-visit this one again.

Still have the 10V charging issue that is stumping me.  Any help on this one is greatly appreciated.