1995 6.5 turbo diesel suburban doesnt start when hot

[Deltaboof1]

Hello 6.5 diesel community, I have a 1995 6.5 diesel k2500 suburban vin number F, 4x4 automatic. I'm having trouble getting it started in hot weather. Wondering if I can get some ideas and feedback it would be greatly appreciated as I had 2 suburbans that did this. Before this it ran almost perfect, no knocking or vibrations. Just some bucking and surging I assume from the injection pump. PMD is brand new with new FSD cooler mounted on the bumper. I have 2 good and healthy batteries putting out 12.7 volts and a healthy starter. In cooler weather (about 5 to 25 degrees Celsius) it runs and starts fine. In hotter weather I cant get it to start up as nice as it usually would. Brand new Bosch glow plugs, light comes on for a good amount of time the GP controller works fine. But when I try to start it, the starter dies down and the cables get hot and it slowly revives itself after about 20 seconds of cranking. Even flashing the glow plugs multiple times. I'm assuming the prolonged starting is due to the injection pump. But why would it be draining the batteries? I've come to the point now where it just wont start for the life of it. Everytime I turned the key the cranking would get slower and slower until it essentially seized up. Batteries were a bit low, charged them up to full and tried again and it's an extremely slow start with lots of draw at the starter. I've had this on 2 trucks but I cant tell what the problem is. Spun bearing? Something is siezed? The pulley system is good and doesnt slip and isnt seized at all. Alternator is good. Please help.

[DmaxMaverick]

Welcome aboard!

This is probably a lot more simple than you fear. Start with a healthy electrical system, focusing on the grounds and cables. The cable size is marginal, failing over time, and act just like you describe. It's usually corrosion inside the insulation near the terminals that you can't see. A good upgrade, and a lot less expensive than OEM replacements, is welding cable. Visit your local welding supplier and have them make a set with properly crimped and sealed eyes.

Also, cranking until it slows down isn't good for anything. Not only does it damage almost everything in the circuit, if it's too slow it won't fire, no matter how long you crank. The IP won't fire the fuel solenoid below about 100 RPMs cranking speed. Your hot wires and slowing starter are a clear indicator. Once overheated, they are never the same, and get worse over time. You shouldn't crank for more than 15-20 seconds at a time, with several minutes between for cooling the starter. An overheated starter requires more juice to turn it, and excessive hot cranking will kill it.

[Deltaboof1]

Will do, thank you, I'll be checking all the wires and will be replacing them asap. Hopefully it works

[N9Phil]

Welding cable is the way to go. I did that to my 95 a few years back and it made a great difference. You might have done your starter in by over heating it. I would definitely start with the welding cable.

[a5150nut]

And if they are side post batteries the stainless bolt trick in place of the stock ends will help too.