i put a 6.0 in my truck last weekend, i have got it to crank 3 times now, it acts like the starter is dragging or the battery is dead but i have changed both and still the same thing. it will spin for just a second and then quit. i drove it around one time that i had it running the motor runs fine, 55 psi oil pressure at idle, no abnormal noises at all. i think it is electrical but i dont know where to start really? are there only 3 grounds on the motor? anything else anybody can think of?

 

Bad ground. I had the same issue. Truck struggled to start but then ran fine. It ended up being a loose ground from the battery to the front of the block. I think there's 5 grounds if I remember correctly

 

yeah i already took all of them back off sanded all mating surfaces and reinstalled them, before i did this all i got was solenoid click and now it just turns 1 compression stroke and bogs.

 

Use a jumper cable to serve as a quick,temporary,low-resistance connection between the engine and frame (or maybe between the starter body and a known,good ground). This might make it crank faster if it is a ground issue. I did this once to confirm a bad ground problem on a 4 cyl truck...same principle.

I've heard these newer (smaller gauge) batt cables are prone to corroding under the insulation;they might look good until you look closely.