Possible Ignition Issue

[myk r sanchez]

http://www.mymopar.com/index.php?pid=27

Do yourself a favor and buy a Power Probe III. It is the best tool you can use for electrical issues.

Man that's a nice piece of tech...

 

[67 Coronet Conv]

So I replaced the ignition switch and got the same reads with the old one.

Red wire
No key-12.5
On-10.7
Running 13.3

car running BR was at 12.8 & 7.2
Coil +7.1 -3.7

Is it common for the ECU to stop working the start working again 12hrs later?

 

[Sixpactogo]

Running the orange box ECU.

I’ll check fuel pump rod and trace wire to see why I’m not getting a full 12 volts on one side of the ballast resistor. Could both of these issues let the car drive for 5 miles than die? When it died, I could see fuel still squirting into the carb.

You more than likely have a bad case ground at your orange box. I had that very same scenario with my 70 Challenger. What happens, is the ECU will get hot and open the circuit inside from not being properly grounded. Paint does not make a good ground. Once cooled down, it will run again until it gets hot. If you have a digital Ohm meter, check between your negative battery post and the case of your ECU. Bet you get a high reading. Should be less than .5 ohms.

 

[67 Coronet Conv]

You more than likely have a bad case ground at your orange box. I had that very same scenario with my 70 Challenger. What happens, is the ECU will get hot and open the circuit inside from not being properly grounded. Paint does not make a good ground. Once cooled down, it will run again until it gets hot. If you have a digital Ohm meter, check between your negative battery post and the case of your ECU. Bet you get a high reading. Should be less than .5 ohms.

thanks, I’ll check this when I get home. Should I run a ground wire from the ecu to a dedicated ground I have about 2” away from the ecu?

 

[Sixpactogo]

thanks, I’ll check this when I get home. Should I run a ground wire from the ecu to a dedicated ground I have about 2” away from the ecu?

I would just scrape some of the paint off around the mounting screws. Maybe add some battery grease if you have some. What ever it takes to get a good case ground.

 

[67 Coronet Conv]

Checked it with a meter and getting 0.3. I’ll put some lock washers on both sides of the screws and remove some paint to make sure I’m getting a good ground.

 

[Sixpactogo]

Wow. .3 ohms is about as good as it gets for a case ground. The ECU ground is starting to sound like not the problem unless it is faulty. It does sound like a coil is getting hot and opening up though. The plate coil in the distributor or your MSD coil could be possible suspects. How about the case ground on your MSD coil? Did you check that case ground?

 

[AJ/FormS]

Taking a different road here;
Is that a recent build or
engine already has lots of miles?

 

[67 Coronet Conv]

Checked the ground between the coil and battery. + is 4.0 and - is 4.5. Don’t know how I would check the coil case ground. Engine is grounded per the beep beep on the ohm meter. Thinking of installing a lager ground wire on the motor to the frame. Coil is brand new too, less than 10 miles on it MSD high vibration

Motor has about 8k on it and is an older rebuild from 2010.

 

[Sixpactogo]

Checked the ground between the coil and battery. + is 4.0 and - is 4.5. Don’t know how I would check the coil case ground. Engine is grounded per the beep beep on the ohm meter. Thinking of installing a lager ground wire on the motor to the frame. Coil is brand new too, less than 10 miles on it MSD high vibration

Motor has about 8k on it and is an older rebuild from 2010.

When I say case ground, I mean the outside body of the coil. Not the + or - studs. If you have a painted engine, painted coil and painted coil mounting bracket, you could have a basically ungrounded coil. When you check the case ground you check between the actual case and battery Neg. Just because your meter beeps does not mean you have a good connection. You could have 20 ohms and still get a beep.