ECU or voltage regulator?

[saintly616]

I am working on a friend's '78 Magnum.Looks stock with a 318.He removed alternator(replaced with 120 amp)and when installing he did not notice that positive wire (to batt)was touching(grounded) the side of alt.
After connecting the battery,some 30 seconds later the cable started to smoke and he disconnect it but too late to save the battery.

To make matters worse,he removed the ECU and harness and not sure of wiring.

PROBLEM:Engine starts normal,runs great for 10 seconds,then very rough,spark knocks(or so it sounds)then dies.If you rev to 2000 or so,will keep running very rough with lots of noise.

From harness (with sending unit leads) I have blue and brown which I believe are run and start wires.I tried switching and disconnecting one,then the other,and seem to function properly.....

QUESTION:Try a new voltage Regulator(heard it click during meltdown) or ECU.

I own a '68 Charger with single ballast and 4wire ECU,this one a double with 5 wire.
Thanks

 

[WP29440SE]

both

 

[saintly616]

Well I replaced both the ECU and voltage regulator but still have the same problem......runs for 10 seconds or so then I hear something click(solenoid sound)then very rough and spark knock.
Anybody ever have this problem and know a solution?

Thanks again

 

[Hemi Rebel]

Is this a lean burn car?

 

[67 coronet]

start it and run it(several times if you need to)and figure out what is making the solenoid sound.if vehicle is lean burn,that could be your problem.

 

[440roadrunner]

is this a lean burn car?

this

 

[WP29440SE]

maybe the starter is staying partially engaged. something to check. can you tell where its coming from? disconnect the vacuum advance while you are at it. hard to diagnose without being there. i have always ditched the lean burn on my later B's

 

[saintly616]

Lean burn is removed,Torker intake with Edelbrock 650.
Engine needs almost 1 hour downtime before you can start it and it runs good for the 10 seconds.

i have tried it a few times to see what's clicking but no luck so far.......

I will try running 12 volts direct to coil to see if it's low voltage problem.

 

[440roadrunner]

I think you probably fried some wires in the harness and are probably going to have to untape the harness from the alternator wire to it's destination to see where it's crossed. The one good thing here, is that these cars do not use full current ammeters, which means that you probably did not carry the problem INSIDE the interior of the car. It should all be right there in the engine bay. This is because none of the alternator high current goes into the interior. This SHOULD be in the circuit from the alternator, around to the battery.



What I don't understand is why the fuse link did not blow, although the same basic thing happened to me on a loaner car

This was a junk Valiant loaner from a San Diego dealer after my 70 RR had been assh#####

I started it up one morning, went back in the shop, and when I came out the alternator was stopped and the belt was slipping round!!!! I made the mistake of loosening the alternator and attempting to turn the pulley to investigate, and it turns out that a diode had fallen inside, still connected!!!! When I tried to turn the pulley, it shorted!!! I got to sit there and was the harness from the alternator to the firewall go fissszzzdeedededddssslllllllleepppppttt!!!!!!! AND THEN the fuse link went fzt-pop??

Called the dealer and said "Send me a different loaner and a tow truck"

 

[Hemi Rebel]

If I understand correctly, everything ran fine till the alternator was changed and the positive battery lead was touching ground? Did the melted wires get changed? Like 440roadrunner says, you will have to open the harness up. when there is a short to ground and you let the smoke out of the wires, it melts the insulation right off, and any wire layed up against it too. That stuff gets hot real fast. You more than likely have exposed wires touching each other. Would probably be easier to replace harness actually. the melted parts at least. Or maybe not. not sure what you have for u pull it yourself junkyards in Canada, but around here there are usally several cars of that era that would be great donors.