Need help from a diesel mechanic

i have a case 1840 skid steer. It will not start start right now. Turn the key and and it turns over like it had a dead battery and stops. Negative batt cable gets really hot. Like welded to itself hot. New batteries, so I know that's not the problem.

I believe it is a 4b cummins engine.

Give me things to check.

 

Is the negative cable securely fastened to the frame. That's one place to start.

 

It's been cleaned/sanded and checked on both ends.

 

Same with the positive cable.

 

From what I am reading there is a short somewhere on the positive side. Try this...
"My suggestion would be to remove the positive cable from the solenoid, and check the resistance from the solenoid terminal to ground. It should be an open circuit (infinite resistance). Check the whole length of the positive cable for cuts in the insulation. Reconnect the battery terminals, and then carefully touch the positive cable back to the solenoid - if it sparks, a short still exists and needs to be found a fixed. "

 

There are a few possibilities;

1) If the cable itself has deteriorated inside the insulation, then it will conduct less electricity (causing slow cranking) and get really hot.
2) Short, as mentioned by @JaCado
3) Starter motor windings have been overheated and are shorting out, causing excessive current and heat
4) The engine is not turning as easily as it should be.

Number 4 is by far the most challenging possibility to address, since it could be caused by any number of problems, including problems with the fuel injection system, big time internal failure, accessory load, etc.

 

Load test the batteries to make sure they're good. Just because they're new...

Supplement the existing cables with jumper cables; if that makes any change, you know you have a bad cable(s) / connection(s)

If that's all good, pull & bench test the starter.

If that's all good... it's probably going to get expensive.