1973 Scamp won't start in start only in run. With a Twist....

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moparmandan said:
No worries. It's all related. Maybe I will learn something. But while we are BS'n what do you mean by doing the ign1 and ign2 thing?
Click to expand...

There are two separate wires that power the coil.
One has power only during cranking and bypasses the ballast.
The other only has power when the key is in the run position and goes through the ballast so the coil runs at a lower voltage so it doesn't overheat.

These two wires are the ones that need to be tied together for aftermarket ignition system like HEI so the ignition system gets 12v in both positions of the key. (start and run)
 
moparmandan said:
No worries. It's all related. Maybe I will learn something. But while we are BS'n what do you mean by doing the ign1 and ign2 thing?
Click to expand...

Confused the issue, see TrailBeast above

IGN1 is dark blue most years, this is "igniton run" and is hot ONLY in run. That goes to the one side of the ballast, and is branched off to feed other switched loads under the hood,

VR "ign" terminal
electric choke if used
some smogg doo dads, including distributor retard solenoid, EGR nonsense some year(s) etc
light blue alternator field

IGN2 is the coil resistor bypass circuit for "start," is brown most years. Goes from a special pole/ contact on the ign switch, through the bulkhead, and to the coil+ side of the ballast

You jumper those two together when using any ignition that does NOT use a ballast
 
moparmandan said:
No worries. It's all related. Maybe I will learn something. But while we are BS'n what do you mean by doing the ign1 and ign2 thing?
Click to expand...
I'm no expert but when you change over to an electronic ignition you can get rid of that ballast resister ,but you still have to power the coil . Thats the ign1 ign2 blue brown wires. I thought I did it correctly 2 yrs ago when I put in the new ignition 'Every thing worked fine. Then I moved the coil to the fender and the 12 v to the coil drops during cranking and comes back when I let go of the key. Thats what I have to chase . Lots of good information here. This problem pops up i bit here so you guys are the Saints of Patience . oh If I got anything incorrect feel free to correct me Jim
 
I would check where you tied the two wires together two years ago can be a bad splice/corrosion.
 
So let me restate this and ask a specific question. We have 10.5 volts at the coil during ign2. We have 6 volts at the coil during ign1. It won't start When cranking until you let go of the key switch back to run. Question is what controls the other side of the coil during crank and run? Is pin 2 of the ECU in play for both ign1 and ign2?
 
halifaxhops said:
I would check where you tied the two wires together two years ago can be a bad splice/corrosion.
Click to expand...
Will do. seems like that would be the place to check first but I butt crimped soldered then shrink tubed it. we'll see Stranger things happen
 
moparmandan said:
So let me restate this and ask a specific question. We have 10.5 volts at the coil during ign2. We have 6 volts at the coil during ign1. It won't start When cranking until you let go of the key switch back to run. Question is what controls the other side of the coil during crank and run? Is pin 2 of the ECU in play for both ign1 and ign2?
Click to expand...
I don't know. I'm lucky mine just drops all the voltage, may be easier to find good luck Jim
 
Ok I'm confused
Are you saying;
That when you return the key to run, from cranking, and while the engine is yet spinning, then it fires and runs?
Cuz that proves everything is normal on the blue-wire side; including the ECU and pick-up,etc. WHEN THE STARTER IS NOT CRANKING
And you have near-battery voltage at the coil, in RUN?
________________________________________________
And you say that in crank-mode you have 6.5volts at the coil positive?
And you have no ballast resistor?
Well that's not right;
It seems like;
1)either the starter is sucking up all the juice,or
2)there ain't enough juice to go around,or
3)there's a dam in the line between the battery and the coil, on the CRANK line,usually the brown wire; and since the starter relay works, I'd guess it would be between the ignition switch and the coil.

The easy test is to jumper from the battery to the coil +, and then hit crank. If it now starts and runs, then you have ruled out the first two possibilities.
 
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If your voltage split is 10.5 and 6
Then either the battery is in very poor shape, or the juice is just not getting to the coil, and 6volts may not be enough to power up the ECU. I know it runs down to 9.5v, but never tried 6

With NO BALLAST, the coil should be seeing within 1/2 volt of battery volts in either position.
If the starter is drawing the battery down, such that only 6v is seen at the coil during cranking.......Something is wrong! A good battery will maintain 10.5 volts during cranking, and therefore I would expect 10V at the coil, during cranking.
Either the battery is NDG, the starter is shorted, or the engine is very difficult to crank.

OOps post #1 says you have a dual ballast
 
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moparmandan said:
So let me restate this and ask a specific question. We have 10.5 volts at the coil during ign2. We have 6 volts at the coil during ign1. It won't start When cranking until you let go of the key switch back to run. Question is what controls the other side of the coil during crank and run? Is pin 2 of the ECU in play for both ign1 and ign2?
Click to expand...

I think you surely must have a wiring problem, crossed wires, something.

the ballast / coil wiring (taking that separate) works just like it always did with points, no change. IN FACT let's say your ECU went bad on the road. You could yank the dist. out, slap in a "points" dist, hook up to the coil NEG, and unhook the ECU wire that had been there and drive on.

This is simplest breaker point circuit I can find:

Dual_Field_Alternator_Wiring.jpg


ONLY difference between this and the newer "4 pin" ECU is that the ECU has a wire going from ECU to coil NEG which switches the coil just like points.

The IGN1 (run), the ballast, and IGN2 are all unchanged, points or electronic.
 
Let's make this even simpler: Here is how we are wiring our conversions to run a GM HEI and a Mopar distributor, no ballast:

4pin-jpg.jpg


The distributor trigger is just like the Mopar ECU.......two wires coming from the coil pickup, trigger the GM HEI

The coil NEG hookup is the same.........the HEI shuts off the coil NEG when the box is triggered, forming the spark (coil magnetic collapse)

ONLY difference here is that there is no ballast............IGN1 and IGN2 are jumpered together because of IGN1 going dead during "crank."

If the ballast was there / used, the wiring for this would be EXACTLY the same as a Mopar 4 pin ECU
 
4 pin Mopar Unfortunately this is poorly drawn. "Existing wire" at far top right is IGN1. IGN2 is not shown, it taps in to the COIL+ side of the ballast. From the ignition switch/ ballast/ coil + is EXACTLY the same as earlier "points" cars

Ignition_System_4pin.jpg
 
Do you have a tach? Unhook it for now. There should ONLY BE ONE WIRE hooked to coil NEG..........the wire going to the box as shown
 
Today's update. Started the day by replacing the starter out of necessity. Couldn't stand all the extra cranking I guess.
Replaced the ECU and coil and ballast resistor just for giggles. No change.
Started doing resistance and voltage checks. Disconnected the ignition switch connector under the dash. 12.5 volts there on the brown wire in crank 12.5 volts on Blue in run. Check resistance on the wires Downstream to the ballast resistor less than 1 ohm. Checked and clean the bulkhead connector just in case.
Reconnected the ignition switch connector under the dash unplugged the connectors from the ballast resistor voltage there 12.5 on Brown and 12.5 on blue.
Plug them back into the ballast resistor check voltage at the coil again 10.5 volts in crank 6 volts in run.
Ballast resistor 1.2 on one side. 5 ohms on the other. Scratching my head.
 
moparmandan said:
Today's update. Started the day by replacing the starter out of necessity. Couldn't stand all the extra cranking I guess.
Replaced the ECU and coil and ballast resistor just for giggles. No change.
Started doing resistance and voltage checks. Disconnected the ignition switch connector under the dash. 12.5 volts there on the brown wire in crank 12.5 volts on Blue in run. Check resistance on the wires Downstream to the ballast resistor less than 1 ohm. Checked and clean the bulkhead connector just in case.
Reconnected the ignition switch connector under the dash unplugged the connectors from the ballast resistor voltage there 12.5 on Brown and 12.5 on blue.
Plug them back into the ballast resistor check voltage at the coil again 10.5 volts in crank 6 volts in run.
Ballast resistor 1.2 on one side. 5 ohms on the other. Scratching my head.
Click to expand...
at the coil again 10.5 volts in crank 6 volts in run.

That's backwards
EDIT
oops no that's right,sorry
 
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One more thing total resistance from under dash flat connector to ballast resistor 1.2 ohms brown wire.
 
moparmandan said:
One more thing total resistance from under dash flat connector to ballast resistor 1.2 ohms brown wire.
Click to expand...
Resistance isn't everything. You could cut every strand of wire except one, of that blue wire, at the coil and ,have still as good as no resistance measureable, yet when you try to pull some electrons thru it ........nada.

FYI
there are a number of factory "welded splices" in your harness. Maybe 4 or 5 I forget. One of them is in the "run circuit". I found mine under the hood, against the firewall behind the distributor. There are about 4 or 5 wires in it; the ignition supply, the regulator feed, the ignition feed, the choke feed, as I recall. I've never seen that splice make trouble,but you should know it's there.
 
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AJ/FormS said:
Resistance isn't everything. You could cut every strand of wire except one, of that blue wire, at the coil and ,have still as good as no resistance measureable, yet when you try to pull some electrons thru it ........nada.
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Understood. Just checking everything I can think to check. And just to be clear on a 1973 Plymouth it's a brown wire at the coil+. Thanks.
 
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And just to reiterate this is Factory 1973 Plymouth electronic ignition wiring.
 
Oh yeah made damn sure the grounds were good at the firewall and at the ECU WITH separate ground wire ran to the base.
 
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TrailBeast said:
There are two separate wires that power the coil.
One has power only during cranking and bypasses the ballast.
The other only has power when the key is in the run position and goes through the ballast so the coil runs at a lower voltage so it doesn't overheat.

These two wires are the ones that need to be tied together for aftermarket ignition system like HEI so the ignition system gets 12v in both positions of the key. (start and run)
Click to expand...

In a 1973 Factory Plymouth wiring only one brown wire going to the coil+ right?
 
67Dart273 said:
Confused the issue, see TrailBeast above

IGN1 is dark blue most years, this is "igniton run" and is hot ONLY in run. That goes to the one side of the ballast, and is branched off to feed other switched loads under the hood,

VR "ign" terminal
electric choke if used
some smogg doo dads, including distributor retard solenoid, EGR nonsense some year(s) etc
light blue alternator field

IGN2 is the coil resistor bypass circuit for "start," is brown most years. Goes from a special pole/ contact on the ign switch, through the bulkhead, and to the coil+ side of the ballast

You jumper those two together when using any ignition that does NOT use a ballast
Click to expand...

It has a ballast, 4-pin. Factory wiring. But since you mentioned it and I'm starting to grasp at straws would it matter if the alternator field connectors were swapped?
 
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