70 Polara Column Connector

[thethee]

A picture would help understand your post

 

[1970FuryConv]

At start, effectively current makes a u-turn at the top of the ballast resistor, thanks to the jumper from one side to the other. If incoming voltage at the brown wire is 10.75 and outgoing at the green/red wire is 6.84, the ECU may not have enough voltage/current to operate during start.

 

[thethee]

I think the blue wire is actually the power supply to the ECU and the red/green is for the mysterious fifth pin. What's the voltage reading on the blue wire in "start"? And in "run"?

 

[1970FuryConv]

I disagree. The blue is ignition run, not ignition start. The ECU cannot get power from ignition run when the key is in ignition start. Ignition run probably uses continuing engine rotation, by momentum, to start the car when the key is released from Start to Run.

J4 provides start power coming from J3A thru the ballast resistor
J6 AND J7: distributor, input and output.
J2E: ignition run
J5: ignition coil primary ground
Without enough power at start, the ignition system does not function because coil and distributor operate thru input power from ECU. If I'm wrong, @Big_John can step in and advise.

 

[thethee]

Maybe I wasn't clear, yes, I agree that the blue wire is ignition run. However, I'm certain ignition run is hot during start as power is back fed through the ballast resistor from ignition start circuit.

With the newer 4 pin ECU's the J4 from your diagram is the missing one so I doubt it's the power supply during start. So I think you should check power at J2E-18LBY* but I might be wrong and you're right and hopefully @Big_John will set us straight.

 

[1970FuryConv]

Maybe I wasn't clear, yes, I agree that the blue wire is ignition run. However, I'm certain ignition run is hot during start as power is back fed through the ballast resistor from ignition start circuit.

With the newer 4 pin ECU's the J4 from your diagram is the missing one so I doubt it's the power supply during start. So I think you should check power at J2E-18LBY* but I might be wrong and you're right and hopefully @Big_John will set us straight.

Then why does the ECU get power from 2 sources at start up? Did Chrysler design redundancy intentionally? If not and power at start only comes from ignition run, the ECU side of the dual ballast resistor is pointless engineering.

 

[Mike66Chryslers]

IGN RUN wire is hot when the key is in RUN position. IGN START wire is hot when the key is in START (starter cranking) position. During cranking, the coil gets full battery voltage but the ECU is powered through the ballast resistor.

 

[Big_John]

At start, effectively current makes a u-turn at the top of the ballast resistor, thanks to the jumper from one side to the other. If incoming voltage at the brown wire is 10.75 and outgoing at the green/red wire is 6.84, the ECU may not have enough voltage/current to operate during start.

I think this is wired wrong. The brown wire (running to + coil) should be 12 volts straight from the ignition switch when starting.

I also really don't like the crimp connectors in the coil primary wires... Run one unbroken wire and lose that potential source of resistance/failure. I'm not a fan of mounting the coil on the firewall on street cars as I think it contributes to failure of the coil wire. I suggested that to someone on a forum once and was told I didn't know what I was talking about, but I digress.. (His car probably still runs like dog ****)

It should look something like this:

What colors are what, I don't know as it looks like this has been changed around. Forget about changing the BR, this needs to be wired correctly as shown. Note the plus wire to the coil.

 

[1970FuryConv]

Maybe I wasn't clear, yes, I agree that the blue wire is ignition run. However, I'm certain ignition run is hot during start as power is back fed through the ballast resistor from ignition start circuit. With the newer 4 pin ECU's the J4 from your diagram is the missing one so I doubt it's the power supply during start. So I think you should check power at J2E-18LBY* but I might be wrong and you're right and hopefully @Big_John will set us straight.

OK, here's the measurements. the one you requested is bold.
2022-01-05 Voltage at Cold Start
· 12.5 V battery charge
· Assistant turning the key to start position, engine cranking, and the ECU connector disconnected, I found the following voltages while the engine was cranking
Coil + & Ballast Resistor

· 10.65 V at Brown coil positive wire
· 10.56 V at Brown starting system wire at bottom left of the ballast resistor
· 8.08 V at jumper wire from top left of ballast resistor to top right
· 8.09 V at ignition run wire, blue, top right of ballast resistor
· 8.09 V at dark green/red power to the ECU wire at bottom right of ballast resistor
ECU

· 8.14 V at light blue/yellow wire, top of ECU connector, right center in pic
· 8.29 V at dark green/red wire, bottom left of ECU connector in pic
Coil + & Ballast Resistor
· Key out of ignition.
· Ballast Resistor 1.5 ohms primary side
· Ballast resistor 5.2 ohms ECU side
· Key in ignition run
· 11.36 V at ignition run wire, blue, top right of ballast resistor. At least .8 L loss in brown 14ga starting wire or ignition switch
· 6.59 V at coil +. Wow!
Results:
· Battery wire to the ignition switch or Brown 14gauge starter wire from the ignition switch has a 2 V drop. This meant not be enough to operate the coil. In addition the ECU is getting 8V at cold start. Again, doubt enough to operate. #1 priority, find the voltage drop. Need to check the bulkhead.
· Ballast resistor cold is supposed to have less resistance. Primary side has 2.5V drop one way and nearly a 5 volt drop the other way. Ballast resistor needs replace
ECU
· ECU: needs to be at warm operating temp before test. Some techs use a heat gun of light bulb to heat the ECU. ECU may require less volts when warm because at optimum operating temp. Could explain why it starts normally when hot.

 

[thethee]

Great info, I think we're getting closer!

· 10.65 V at Brown coil positive wire
· 10.56 V at Brown starting system wire at bottom left of the ballast resistor
· 8.08 V at jumper wire from top left of ballast resistor to top right
· 8.09 V at ignition run wire, blue, top right of ballast resistor
· 8.09 V at dark green/red power to the ECU wire at bottom right of ballast resistor

Your description and picture don't match. Assuming bottom right, blue connector is your starting wire (as it should be) there is no way you should be getting 8.09 V at the bottom left, red connector as current would pass through both sides of the ballast resistor to get there. As you say that the left side (correct?) of the BR is reading at 5.2 ohms I'm starting to think you might have a short or wrong connection somewhere. Can you confirm the red/green wire is intact and only connected to ECU and bottom left of ballast resistor?

 

[1970FuryConv]

Great info, I think we're getting closer!
Your description and picture don't match. Assuming bottom right, blue connector is your starting wire (as it should be) there is no way you should be getting 8.09 V at the bottom left, red connector as current would pass through both sides of the ballast resistor to get there. As you say that the left side (correct?) of the BR is reading at 5.2 ohms I'm starting to think you might have a short or wrong connection somewhere. Can you confirm the red/green wire is intact and only connected to ECU and bottom left of ballast resistor?

Description is right:

In Picture: working counterclockwise

• Bottom right is starting wire
• Per wiring diagram: my ballast resistor has jumper wire from top right to top left in picture. Top right spade serves no other function.
• Top left blue wire at ballast resistor, ignition run is power feed to ECU at start and run although input power to ECU is reduced at start by the right side of the resistor.
• Lower right dark green/red wire at ballast. DG/R connects to nothing else beside the ECU and provides power only to the ECU. I have taken the entire engine compartment wiring apart. The second side of the dual ballast resistor exists solely to reduce current through DG/R especially when ballast resistor is hot.
• Early 5 pin ECU has 2 power feeds
  
• Later ECU has 4-pins and deletes the auxilliary power feed DG/R wire and thus the dual ballast is replaced with single ballast.
• My conclusion is the same
• Primary Problem: 2V drop across battery. ignition switch, starting wire system
• Secondary problem: primary side (Right side in pic) of ballast resistor is providing 2.5V drop when resistor is cold. This is too much cold resistance, indicating age and wear. Not helpful to cold starting.
• Respectfully, Ben

 

[thethee]

Thanks Ben, in that case I can only reach the same conclusions as you do and I hope swapping the ballast resistor and fixing the voltage drop do the trick for you. Wish I could've been more helpful.

Theo

 

[3C's & a D?]

I would move the coil. The high voltage main wire is really close, possibly touching? The two low voltage components right beside it.

 

[1970FuryConv]

Thanks Ben, in that case I can only reach the same conclusions as you do and I hope swapping the ballast resistor and fixing the voltage drop do the trick for you. Wish I could've been more helpful.

Theo

I would move the coil. The high voltage main wire is really close, possibly touching? The two low voltage components right beside it.

Replacing the ballast resistor with a new Standard BR did not change the voltage readings. Beyond that, I haven't had time to work on the Monaco. Timing chain job on my DD pickup, plus an impending kitchen remodel have taken up most of my time.

There is no coil mount on the intake. I don't see coil secondary wire touching, nor does it have any damage that would cause a short. Is there some issue with the coil secondary wire being close to primary wires?

 

[3C's & a D?]

I wasn't thinking a short, and I'm probably overthinking it, however the coil to distributor wire has alot of electricity running through it, and while the insulation is shielding and suppressing it, there is almost certainly a field around it. I can't see it effecting the ballast resistor, but possibly the ECU? That doesn't support the hard cold start/good hot start problem though.

You should start a new thread describing your problem to get more minds on it. This one was started with a different question from a different member.

 

[1970FuryConv]

You're right. I stole a thread. Generally a bad idea, not to mention discourteous.