Today, I pulled the truck in to change the oil, when finished, the thing would crank but not start. After checking the lift pump and the connections on my new heath PMD unit, I tried to start it a few more times, but the battery started getting weak. I connected the charger, put it on the 200 amp engine crank setting and the truck fired right up. My question is do I have a hot start issue that cooled down a little or a voltage issue? How sensitive are these trucks to low batteries, because the truck seemed to crank pretty good when I tried to start it the first couple of times.

they seem to be very sensitive to bad batteries. Clean both ends of all your battery cables. Drop it on the charger tonight and see how it runs the next couple of days.

It has been running kind of rough since I put the new exhaust on. Still seems to have good power while towing but idles a little rough up to about 1700 rpms.

check the main wiring harness where its tight against the pipe between the coolant resevoir and exhaust downpipe

look for wires rubbing through

No rubbing, wires are well away from exhaust and other friction sources. I also recently installed the Heath isolator, I know it has a new resistor in it, would the fact that the new resistor doesn't match my old resistor matter?

that doesnt matter.

Didn't think so, just grasping at anything at this point. The truck definitely pulls better now, but it just seems like it idles rough. I went from 45mph uphill with my fifth wheel to 60 mph and almost 200 degrees lower egt while doing it.

did you remove and clean up the battery cables like I suggested?

Yes cables are clean and tight. Going on a 300 mile trip today, pray for the old truck! I can't be late. I've got 8 ounces of 2-stroke oil and 8 ounces of power service in a full tank of fuel, nice, tight battery connections, new exhaust, new isolator, and hopefully today I'll get my medical release to go back to work! I never thought I'd say this, but I miss work! It's been 2 months.

Should be 16 ounces of each, for some reason I can't edit.

How old are the batteries?

Do a search for some old posts by canadianrigger....he had problems caused by a PMD resistor value....it was an oddball problem but it existed nonetheles....

Batteries are between 2 and 3 years old.