Truck won't start

It shouldn't be cranking slow with new batteries plus you had a charge on them. Could be bad cables going to the starter or starter itself from cranking to much, but first get the air out of the lines and go from there. My truck was cranking slow also, bought 4 batteries and still was cracking slow ended up my starter was cooked from cranking on it for 2 days.

 

I have an 07 379 with Cummins ISX Motor.
Noticed a while before any issues that she was slow to start but always fired up. When I say slow I mean the crank just seemed slow.
First bit of trouble I had was after running for 4 hours or so and turning truck off that she wouldn’t start immediately back up.....parked short of where I wanted to be once and I couldn’t get her started to move the 4 feet. She cranked but it was like I had a bad battery. Waited 10 minutes and the crank got faster but still wouldn’t start. Waited 40 minutes and she started with still a slow crank.
Replaced all 4 batteries and it didn’t improve....slow to crank and after running for a bit she wouldn’t fire right back up.
Round 2 was to replace the starter and exact same results.
Round 3 I wasn’t having any part of and took to dealership. They replaced all of the negative cables connecting the batteries and issue fixed. Even the slow crank is gone.

 

I had slow crank and it was a bad battery once and the next time was the switch right above the batteries on the volvo. I bypassed that to test and cranking was unbelievable. I ended up eliminating that switch, I don’t use it anyway. It had a slight voltage drop between multimeter to the batteries and dash voltmeter.

 

G1 k was the truck cranking slow before this all started?

 

Yeah I would have to say that's the problem. Did it crank slow before?

 

Think you found the problem.

 

Do you only have one positive cable going from batteries to starter? You really should have 2 positive and 2 ground

 

Pretty sure you found the problem.
Don’t look at it like you bought 4 new batteries for nothing, they eventually would have needed replaced anyway.
Get the new cable tomorrow and let us know how you made out.