wiring harness meltdown..

[chargerdon]

Today, worked with a buddy...and we were able to plug in a new ignition switch into the switch connector at the steering wheel.  To see if that is the problem...  BUT no get the same results.   I.e   Car will crank from the switch but not start.   So doesnt seem to be ignition switch...   

I can make the car start in two different ways.. 
1) Leave ignition turned to on...and jumper the starter relay to make it crank and she starts right up.    So the "RUN" side is good.

or

2) jumper wire from battery to the brown start wire on ballast, and then either crank via the key or the starter relay jumper...   and she will start.   

So to me start way 1 and 2 both mean that from the ballast resistor back is good (including when attempting to start), and the run side is good...   Start side

If i leave the starter relay wire off, and use voltmeter right at the ballast brown wire i will read between 11.56-12.2 volts...  and if i leave starter relay on so she cranks then from the key...that voltage will drop to 9.5  (i guess the starter itself drops the voltage that much).   SO IT SHOULD start...   

new ignition switch made no difference.   

another test was using the new ignition switch...  i jumpered at the back of the switch the blue run, and brown start wires... then turned the ignition to crank...and she starts..   

One really weird reading i get, is with bulkhead connector removed, and ignition switch in off, if i measure voltage right at the bulkhead for start i read about .95 volt...it should be zero...   if i turn the ignition switch to start it jumps to 12.5...   i am worried about that .95-1.0 volt reading with key off.   Could the wires in passenger side of bulkhead have been damaged?    plus reading good voltages is nice but no guarantee she will pass enough amperage. 

That is my next step...to pull passenger side bulkhead down far enough to examine those wires for "melt" damage.   

any other suggestions?

[734406PK]

CORRECTION...   If i turn the key to RUN not start and jumper the relay block to make it crank it will start !!   

Knowing this i then pulled off the start wire from the relay so engine wont crank, and also pulled BOTH ballast resistor connectors off.   With key in RUN i have power on the blue connector that jumps to the other side.   AND like .3 volt on the other ballast connector (the one that gets the start switch wire).    If i turn the key to Start then the power goes to zero on the RUN ballast connector and i get about 11 volt at the start ballast connector.    Sounds good...but with both connected on RUN i show 11.5 volt at the positive coil connector, but when i turn the key to start The voltage drops to zero at the coil positive connector.   No wonder it wont start...but why??   Do i have a short somewhere, or is the voltage i see on START connector phoney...i.e shows 11 volt but maybe no amperage??  i.e not passing enough current to run the coil and ecu ?   

Check the voltage at the coil positive terminal with the key switch in the start position. You should have battery voltage there while cranking. The brown wire that is hot while cranking at the ballast is also common to the coil positive terminal.

[chargerdon]

734406pk    Yes i have that diagram...   putting multimeter on the brown (start) lead at ballast with starter relay disc, i read 11.75 volt...with starter relay wire connected and engine cranking...i read 9.6 volt...   that should be more than enough to start car.   But it cranks and wont start.   But my theory is even tho i read good voltage...and there enough of a connection for a good amperage draw? 

Tomorrow, i'm disconnecting the bulkhead connector and putting three jumpers...into the bulkhead on firewall...   
1) to Starter relay to get cranking
2) pin 23 (start) directly to brown start wire on ballast.
3) pin 22 (run) directly to the blue (run wire) on ballast.

The above will eliminate my repaired engine harness to bulkhead...  and try to start ...if she does, then it must be somewhere in my repairs.   If she doesn't (and i'm betting it wont) then it has to be between the bulkhead connector and the ignition switch flat connector.   Now if that is the case... im going to have to disconnect all of the connectors at bulkhead on engine side...and show the entire thing in and hope i can pull it down till i can see any obvious damage to the wires on that side.   YUK...  I just love working on my knees...

[734406PK]

Sounds like a good plan. I was reading one of your previous posts (quoted) and if I'm understanding it correctly, you have power at the brown wire ballast connector but zero volts at the coil positive. Is this the case?

[chargerdon]

No...  I have power at both...  thats why its so baffling...it should fire..   Im still thinking that while i show volts...there isnt enough amperage thru the brown wire.   

[dodj]

Wow. Difficult to deduce a logical clear path to your problems.  Some of your tests seem to contradict themselves at different times. So I'm thinking you must have additional overheating problems within your wiring. Perhaps the wiring at your B/H connector on the cabin side? You appear to have eliminated all other components as being the problem.

[73440]

I had to wire the ballast resistor as the photos show to get it to start.
I have not checked or compared it to a wiring diagram to understand why it needed wired like this to run.
Plan to spend some time this week reviewing if the way I had to make the connections is actually per standard wiring.

[734406PK]

No...  I have power at both...  thats why its so baffling...it should fire..   Im still thinking that while i show volts...there isnt enough amperage thru the brown wire.

Ok so you have battery voltage to the coil positive terminal and the brown wire on the dual ballast while cranking, just needed to be 100% clear on that. You also need to see battery voltage (or slightly less due to the ballast resistance) to terminal #1 of the ignition ECU while cranking (VIA the run ballast connector). The brown wire needs to be connected to the low resistance side of the ballast (.5 - 1.2 ohms).

Also- do you have a 5 pin or 4 pin ECU?

[734406PK]

I had to wire the ballast resistor as the photos show to get it to start.
I have not checked or compared it to a wiring diagram to understand why it needed wired like this to run.
Plan to spend some time this week reviewing if the way I had to make the connections is actually per standard wiring.

It looks like you are missing a jumper wire in the ballast connector. The dark blue wire (Hot in run position) and the light blue (power to ECU terminal #1) need to be connected together and installed onto the ballast low ohm side with the brown wire. This is where the run and start circuits combine to power the ignition system.

[chargerdon]

734406PK  and anyone...   OK there have been a lot of posts...let me recap all of my tests and efforts.

All started with a meltdown of a couple of wires on the engine wiring harness.   I pulled harness and replaced any burnt wires (primarily the main "run wire" into the junction point in harness, and the start wire right beside it).  I then continuity tested each and every one of the 8 Bulkhead connector wires and the main points on the engine side 8 pin to connector.   

After repairs put harness back in and the engine will crank from the ignition key but not start.   I can make the engine start by two methods.  1) with key off, run bypass wire to brown (start) wire on ballast direct form pos post on battery, and then force crank by jumper wire on starter relay.  or 2) with key on jumper the starter relay for force crank.   Either way she will start.   

Ok, today I tried a new ignition switch connected in at the connector (not into the steering wheel) and pretty much got the same results so I can rule that out.   However, i was getting some inconsistencies when testing like this, so went back to the original ignition switch in the steering wheel, but, i also cut out the Brown (start) wire on both sides of ignition switch connector and spliced it together..   Inconsistencies gone.   

Second I have the 5 pin ECU and have tried a spare for it, and a spare ballast resistor...   Same results.   

My system is wired like the diagrams a and b found on my mopar for 74 challenger (http://www.mymopar.com/downloads/1974/74ChallengerA.JPG).    The problem with that diagram is that it doesn't show the ballast NOTCH so you cant figure out which side of the ballast is the 1.5 ohm side and the 5 ohm side.   However if you look at the 5 Pin ECU picture in http://www.chargerr.com/Ignition/Ignition.htm it logically is like that one.  In other words i have the Brown (start) wire on the 1.5 ohm side, the green ecu wire on the 5 ohm side, and the little jumper across the 1.2 and 5 ohm with the blue (run) wire.   (see my picture).   

Now here are some readings taken today:

Volts
My Batt shows 12.35 volt.  Below tests were done with starter relay wire off so no cranking.
with key in RUN   i show at the blue post on the ballast 10.85 volt and at the brown wire 4.9 volt
with Key turned to "start" Blue wire at ballast shows 6.88 volt and brown wire 10.8   (note if i pull the Blue connector off of the ballast then i show 12.2 volt at the brown wire so i assume that the current draw from the choke heater, VR, alternator field, and ECU account for the voltage drop at the ballast).

AMPS
disconnecting neg cable from battery and running thru amp meter between negative cable and negative battery post is show
key off  .001 amp
key to run 5.1 amp
key to start 5.1 amp.

One interesting point is that my multimeter shows 5 amp draw at battery, for both run and start (no cranking as starter relay wire pulled), but with battery hooked up and looking at my amp meter in the car, when turning key to run i show some discharge as expected, and when turning it to run an even deeper discharge...    That doesnt agree with multimeter hookup. 

Ok, so i've got volts and amps on the brown wire SO WHY THE HELL wont she start?

Lastly, as a test not trusting my multimeter,  i have two DC electric motors...  Taping off of the ballast brown wire and into the motors (wired in parallel) and then to neg battery they both run when key turned to start...so amperage is there.   Running thru my amp gauge the two motors draw about 4.5 amp..   So i have at least that amount of current capable at the brown ballast.   

Also, i have ohm continuity tested the Pin 1 on ecu connects with near zero resistance to the blue, start wire, and the dk green red wire other side of brown wire goes to pin 3 on ecu (counting clockwise from pin 1...pin 1 being the top of the mopar pentastar. 

Lastly, while it didn't pull the cabin side of the Bulkhead connector off, i was able to look with a strong flashlight at it (talk about discomfort twisting yourself) and it LOOKS 100% clean.   I.e no visible signs of overheating or melting or black spots etc.   

I'm stumped...     

[734406PK]

Quote:

Volts
My Batt shows 12.35 volt.  Below tests were done with starter relay wire off so no cranking.
with key in RUN   i show at the blue post on the ballast 10.85 volt and at the brown wire 4.9 volt
with Key turned to "start" Blue wire at ballast shows 6.88 volt and brown wire 10.8   (note if i pull the Blue connector off of the ballast then i show 12.2 volt at the brown wire so i assume that the current draw from the choke heater, VR, alternator field, and ECU account for the voltage drop at the ballast).

You are dropping about 1.5 volts @5.1 amps through your key switch circuit for some reason. 6.88 volts on the blue wire while in the start position is very low also for an instant reading. Try jumping out your ballast resistor on the brown to blue side. This will apply battery voltage to the coil positive terminal and pin 1 of the ECU while cranking. 6.88 volts (and even lower with the starter draw) may be too low to fire the ECU.

[chargerdon]

734406pk...  yes, if i jumper the brown at blue wires at the ballast it will start on key !!  (of course i cant leave it that way without suffering premature wear out on the coil).  By doing this im showing 9.9 volt on brown wire with key in run...vs 4.89 volt without the jumper.   

So what does this mean??   

Also,  To try i took the 4 pin ECU out of my charger...which i think is good...but..who knows...as the charger is down right now..    and with it in i cant get the car to start no matter what i do...   From what i read you should be able to put a 4 pin in the 5th pin in ecu wont be functional, but, it is supposed to take care of that internally...   or with a 4 pin do i have to do something else??   Is distributor the same on 4pin vs 5 pin...   I know ballast is different but that side (5 ohm) simply should not matter with the 4 pin.    Am i missing something?

[HP_Cuda]

I believe you have something wired backwards.

The intent is when you turn the key to start the car you have FULL VOLTAGE 12.6 or very close to it. Once the car is running the ballast steps in and drops the voltage to 8-9V - this is done so the coil will have a long life and not die because you are running it at 12+V all the time.

You need full voltage to start the car so check all connections in each step (key on, ignition start, run) and report voltages back here. As well, when you are going through this give voltages at each side of the ballast and the coil.

Hope this helps a bit.

[chargerdon]

HP-Cuda...  yes...ive been working on it...somewhere there is a voltage drain.   As an experiment i measured amperage at the battery with key in run...   it draws 5.1 amp... like i said earlier.   But,  If i disconnect both the choke heater wire, and the VR to take alternator off that amperage draw drops to about 3.6 amp.   So those two draw about 1.5 amp.   If i leave both of them off, the voltage rises and the car will start from key. 

Or if i jumper the blue (run) wire on ballast to the brown (start wire on ballast) effectively taking out the 1.2 ohm resistor to not only the coil but also to the ECU...she will start on key.

Lastly, if with battery a little low and battery charger on it...i will read 14.3 volts at the battery and an extra volt or two at ballast resistor and she will again start from key.    734406pk told me it takes at least 9.6 volts to the ecu pin one to get it to fire the coil...  i read that, but, when cranking it drops below that thru the brown wire...   

So, my conclusion is everything is wired correctly, but, somewhere there is a voltage drain...just a little...enough to not fire the ecu and cause no start...   its that close to working..   Now the hard part...finding the current (voltage loss).   

[HP_Cuda]

Well you can do what I need to do pretty soon.

Remove the negative battery cable and while the key is on check the voltage between the post and the disconnected negative cable. This will show the voltage drop you are experiencing. You can also set your multi-meter to check amperage and see what kinda draw that is as well so either way will help you diagnose this problem. Next you start pulling fuses one by one to see which culprit is giving you problems. Then fix the problem and presto chango you are in business!