Was running but now after pulling alternator wire, it won’t run

[1969dodgedartswinger]

Hey everyone! I have been doing a lot of reading through a few of the different threads. Yesterday working on my 69 dart 340 with a 6AL box, the alternator wasn’t charging (I just ordered my third one). in the mean time I put the original back on which also doesn’t work. My father and I tried seeing if there was a draw on the car and where it could be coming from. He pulled the wire off the back of the alternator and I started the car. It ran for a couple seconds then shut off and won’t restart. The 6AL box flashes 5 times showing it’s in working order and firing. But the car has absolutely no spark. I also have ballast resistors on the car which I am going to bypass. Can anyone help?

 

[crj1968]

You still have the alt wires going into the Ammeter on the dash? take off the main alternator wire. leave it off. Run a NEW thick gauge wire from Alt to Battery positive and see what you get.
How are you determining your alt doesnt work?

 

[crj1968]

Also check MSD website for wiring instructions. I dont run one anymore, but have in the past and don't recall it using a ballast. let me back up a second. So the car cranks fine, but you have no spark at coil?

scroll to post #12

MSD 6AL Wiring and Ballast

I know this has probably been covered before but I need confirmation I am doing the correct thing. Can I just join all these wires together along with the Red from the MSD box. I am fecking hopeless with wiring and dont want any damage as I have screwed up a Ready to Run before. Before...

www.forabodiesonly.com

 

[67Dart273]

Just exactly which/ what wire are you talking about?

The alternator should have nothing to do with whether the engine will start and run

Check that with the key in the run position, that the MSD is getting power to the "small red." Then while watching the voltmeter, crank the engine USING THE KEY. Again the small red should be getting power

ALSO make CERTAIN the "big rid" is getting power at all times, and that the large black is grounded

There is a troubleshoot procedure over at the MSD website

 

[1969dodgedartswinger]

You still have the alt wires going into the Ammeter on the dash? take off the main alternator wire. leave it off. Run a NEW thick gauge wire from Alt to Battery positive and see what you get.
How are you determining your alt doesnt work?

I checked using a multimeter. Alternator is only showing battery voltage. I also did the negative battery cable trick. If you pull the negative and the car shuts off it’s the alternator. Also I don’t have anything going to the voltmeter in the dash.

 

[Phreakish]

I checked using a multimeter. Alternator is only showing battery voltage. I also did the negative battery cable trick. If you pull the negative and the car shuts off it’s the alternator. Also I don’t have anything going to the voltmeter in the dash.

Please be specific about which wires were checked. It matters a whole bunch. 'alternator shows only battery voltage' doesn't really say as much as one might think.
There's the big charging stud on the alt, and two field wires. The field wires are controlled by the regulator. Depending on which generation of voltage regulator you have and what generation of wiring is in your car, the field could be the whole issue.
Pulling the negative can be misleading. A bad regulator, a bad field wire, or improper wiring could all result in it not running. Doesn't mean the alt is bad in all cases.

Have the alternator bench tested to rule it in/out. If it checks good, we can proceed from there.
In the meantime, do you know if the voltage regulator is correct? Was it recently replaced along with the alternator? Can you take photos and post them of the regulator?
I'm not an expert on the timelines, but Chrysler had a single-wire regulator up until around 1969, and starting in 70 had a 'dual field' style. I've only ever dealt with the dual field style, and many auto parts stores will sell you an alternator for your single field car setup for a dual field regulator. Do a search and you'll find a ton of info on that, but you really need to investigate your car to determine which system it has. It's not uncommon for previous owners to have swapped out to the later style at some point in the last 50 some years.

As others have said, there's no reason for the alternator to have an impact on whether the car will start and run unless something was shorted and caused a problem. I don't like disconnecting the battery from the system while it's running, especially with aftermarket ignition, because I've seen that result in hard to trace damage in the past.

For now, I'd bypass the MSD using the factory ignition and see if it suddenly runs again. MSD doesn't have the greatest reputation for reliability these days.

 

[67Dart273]

I checked using a multimeter. Alternator is only showing battery voltage. I also did the negative battery cable trick. If you pull the negative and the car shuts off it’s the alternator. Also I don’t have anything going to the voltmeter in the dash.

No. Do not ever do this. This is an old wives tale and can cause damage to electronics, AND IT IS incorrect, EXAMPLE:

A: "Let's say" the alternator is perfectly fine, but the engine is idling a bit slow, and the alternator is simply turning too slow to provide enough output. You pull the battery cable and the engine quits ---you FALSELY conclude the alternator is not charging.

B: "Let's say" the alternator has a couple of bad diodes and so is operating at greatly reduced output. Maybe less than half it's rated current. You yank off the cable, the engine stays running, and you FALSELY conclude that the alternator is fine.

By the way for this fake false test, it does not matter if you remove the hot or ground battery cable.

 

[66 Valiant wagon]

Do you have a wiring diagram? You need one. The main feed for most of the car runs through the Amp meter in the dash. Has it already been bypassed?

 

[Mattax]

Do you have a wiring diagram? You need one. The main feed for most of the car runs through the Amp meter in the dash. Has it already been bypassed?

Yes.
Not true.
Probably not relevant.
What is relevant is what the ammeter is showing.

Alternator is only showing battery voltage.

The alternator output wire and the battery positive should always be the same voltage.
Engine off, system voltage is battery voltage
Engine running, system voltage should be alternator output voltage. But if the alternator can not produce enough power to run the electrics, then voltage will drop to battery voltage. Its easy to see on the ammeter if the power is comming from the battery as it will show discharge.

When the engine is running and the alternator system is working properly, power comes from the alternator. The ammeter will be centered, or if the battery was low, it will show battery charging.

'All power goes through the ammeter' is false, and misleading when diagnosing a power feed problem.

 

[Mattax]

Hey everyone! I have been doing a lot of reading through a few of the different threads. Yesterday working on my 69 dart 340 with a 6AL box, the alternator wasn’t charging (I just ordered my third one). in the mean time I put the original back on which also doesn’t work. My father and I tried seeing if there was a draw on the car and where it could be coming from. He pulled the wire off the back of the alternator and I started the car. It ran for a couple seconds then shut off and won’t restart. The 6AL box flashes 5 times showing it’s in working order and firing. But the car has absolutely no spark. I also have ballast resistors on the car which I am going to bypass. Can anyone help?

Ballast resistor is irrelevant to the MSD 6 series.

Not sure why you want to look for power draw, but you can use the battery power and the ammeter.
Engine off is all that is needed to take the alternator out of the equation.
Ammeter should show zero discharge. If it shows discharge, then something is drawing power.
Open the door for example and watch the ammeter as the dome light turns on.
The only things it won't show are the starter and starter solenoid and the MSD draw if the MSD's power feed (heavy red wire) is connected at the battery positive or starter relay junction.

If there is no discharge with key off, then you could put the key into accessory and see if anything is drawing. That will cover all the circuits except those needed to run the engine.

1969 Power circuits were like this

I suggest piggybacking the MSD on/off wire to one of the ballast resistor terminals. It doesn't really matter which one, but they suggested the Ignition run side.
Make sure the ignition run circuit has good connections to the voltage regulator ignition terminal as well as the ballast resistor.

You can connect the MSD power to either the battery positive circuit or the alternator output circuit. Alternator output line will keep the ammeter reading correctly. In my experience with an older MSD 6T this works fine.

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