Cummins N14 Died, Now I have Slow Crank. Help!

Here is the scenario, the truck is a 1996 International 9400 with Cummins N14 Red Top. The truck died while driving after crossing a set of rough railroad tracks. When I attempted to start the truck all I would get was a "clunk" from the starter. The sound of the starter gear engaging the flywheel but not being able to turn it. After pulling over to investigate I noticed a negative battery jumper wire burned pretty badly. Got the truck towed home and began to troubleshoot.

So far I have replaced all 4 batteries, all positive and negative battery cables along with the main leads for the starter two positive and one ground. I have also replaced the starter ground strap that connects to the frame and have replace the battery to frame ground wire also. I have cleaned and sanded all wire connector ends that I can find. To ensure that the starter was not the culprit I replaced the the Delco 42mt with a new 39mt starter.

So far nothing has changed in regards to the starting system with the exception that while the battery charger is hooked to the truck the engine will try and crank but very slow, it makes about a quarter turn before it quits. When KEY is on, all dash gauges sweep, check engine and stop engine lights come on, volt meter reading around 12-13 volts. When I jump the magnetic relay mounted to the cab I get the same thing. Slow crank or either a clunk as if the motor was locked.

My next thought is to dig into the engine wire harness loom and search for any bad or burned wires there. I am also going to have a load test done on all the batteries. Any insight or suggestions to what could be the reason why the engine will not crank over?

Much appreciated.

 

Replaced starter, and all starter wires, including ground strap.

 

I have two batteries charging overnight on the battery charger. My plan was to swap those two in and dig deeper. On the Delco 39MT do I jump the starter by connecting a positive lead to the magnetic relay on top of the starter solenoid?

My next thought was to try and roll start the truck by pulling it and popping the clutch in 5th gear.

Oil at the dipstick looks ok, I have not drained the pan or pulled the valve covers as these will hopefully be a last resort.

The N14 Red Top has ECM, which from my understanding is working or at least getting power due to the gauges sweep when key on and the check engine and stop engine lights coming on.

 

The starter is not controlled by the ECM. The starter is the link between the batteries and ignition. I have to admit that I am stumped so far.