Negative battery terminal smokes when turning over the starter?

FIXIT12090

MEMBER
1987 FORD MUSTANG
V8
2WD
MANUAL
80,000 MILES

Ive had the car for 3 years this is the 2nd motor ive put in the car we pulled it out of my friends car it ran fine I did a cam/head swap on it well we got the motor down in the car and it turns over good but it wont start and if we turn it over for 5 to 6 sec the negative battery terminal will smoke and get very hot I have ran out of thinks to try we got a new battery checked all of the grounds (i dont no what im missing)

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

The cable is smoking because the cable is getting hot.

It is getting hot because the connection is not clean and tight and there is too much current getting back to the negative post. This means there is still resistance in the circuit.

I would suggest we start with checking the battery and finding out if the battery is good even if it is new. If the battery is good, then we need to remove and clean the terminals.

https://www.2carpros.com/articles/car-battery-load-test

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

If they are clean and tight and it still smokes, then the cable itself has failed and requires replacement.

You can prove this by testing resistance on the cable. You do this by removing it at both ends and checking the resistance. This guide will help with this:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please run through this info and let me know what questions you have.

Thanks