Mechanic having trouble after a rebuild

Good Day,
I bought a Dodge Magnum with a totally rebuilt engine from one of my closest friends who ran into electrical problems post-rebuild. My friend owns a shop in town, his father owns 2 more, he’s a 3rd gen mechanic and builds race cars as a hobby. His fathers “electrical” specialist came down to help w/the problem and found a bad connector to the ECM. It’s killing batteries if that helps, the engine runs perfectly (I’ve seen it). Anyone run into electrical hiccups following a rebuild? Spare me the comments about my friends prowess until you’ve seen how many race cars he’s built from the ground up, complete with custom suspension and roll cages, nitrous tanks…he’s long acknowledged electrical is not his strong suit. Thank you

You posted this problem once before. You didn’t provide us with enough info then or now…

WHAT is killing batteries? The ECU? Or something else?

So is killing the battery the only symptom now? Your previous post on this listed more problems than that. Are the others fixed now?

You can tout the accomplishments of the mechanics all you want but the bottom line appears to be that they cannot fix the car… and they are standing next to the car laying hands, tools, and scanners on it.

We are out here on the internet getting 2nd hand info from you (who admits you don’t know that much about modern cars) about the problems. This is like me passing along advice from a doctor to another doctor about how to remove an appendix. Not likely the patient is going to have a happy outcome!


Car blew up motor. Ran good till blow up.
Won’t run with new motor.
We know it electrical.

I understand, I appreciate you taking the time to read my post and reply just the same. All I know is the
motor is running perfectly (I was under the hood last week, it ran like a top) but my friend was having
trouble solving a battery drain…and the Mag has a boat-sized battery, I installed a new one before he began the work His electrical guy chased the trouble down to a connector to the ECM, he installed it Friday and told me it should be done by tomorrow, I’m just wondering if it will relearn on its own or has to be reset with specialized equipment my friend’s shop would not have. Thanks

To play “Devil’s advocate”, I’ve heard it will be ready tomorrow before, I also know my friend well enough to
know he doesn’t always go by the book, and if the ECM needed to be properly reset by Dodge, he wouldn’t do that, he’d try to work it out on his own. He does have pricey scan tools, but certainly not one made for a Dodge

If this ’ Mechanic Friend ’ is not going to do proper repairs then you are just wasting time . Which you have done already with this vehicle.

If all he did was replace a connector it should be fine. Assuming, of course, there aren’t any other problems.

Thanks Sir, I think if there are any further issues I will take the car to an auto electric shop, pricey but this has taken long enough and I’ll know he’s simply out of his depth. For years he’s admitted electrical was never his strong suit…clearly

I plan to retrieve it regardless of tomorrows outcome and take it to an auto electrical shop.

I didn’t understand that was the case, I’ll take it elsewhere if tomorrow doesn’t go as planned. Thank you

Hi wyattspoppa:
Several thoughts come to mind.

Have you verified the battery is correctly getting charged when the engine is running?

What is the voltage at the battery during idle and at a higher rpm (2000)?

If the battery is getting charged correctly, then starting with a good battery, the question becomes:

  1. Is the battery “getting killed” after the engine is shut off?
    If so, go through the normal triage of inserting an inline current meter at the battery to determine the amount of drain, and then start pulling fuses and open circuits to determine the offending circuit.
  2. If the battery is “getting killed” while the engine is running, then please report back with the voltages at the battery at both idle and at 2000 rpm.