FLD 120 won't crank when cold

Connect a multimeter between the positive battery post and the starter. Should read close the zero volts when you crank. Any voltage that you see on the meter is considered a voltage drop.

Check from the battery positive post that is furthest from the starter. Also, check at the other side of the starter solenoid (leading into the starter body) as well. Then do the same for the negative side. Negative battery posts to the starter frame.

Generally a maximum of 0.7 volt loss (0.5 volts for cables and 0.2 volts across the starter solenoid) is permissible for the entire starter system.

 

First thing to do is check the terminals. They often get loose. Give them a twist and tighten if loose. If they’re the original style, the ends may be corroded under the plastic covering. Next, look for a positive cable, (probably have 2 of them) that’s worn through the sheathing and grounding on metal. Often the battery box itself. If so, tape it up, protect with old heater hose. Might want to check distilled water in those new batteries. One of those things has always worked for me. New cables are best on an old Truck. You can always run a set of jumper cables from positive battery to positive on starter. See if it cranks better.

 

Warms and colds often indicate a loose or corroded ground strap. When cold the metal shrinks leaving a loose connection, then once the high amp draw of starting warms it up the metal expands and makes a tighter connection. Corrosion works similar.
Since the starter was recently replaced, go to it and check the connections there first as one or two of them may have loosened.
If you drive in much salt, any cable that were made using a shrink tube at the crimped ends, often leak and salty water will get behind the shrink tube and make a mess that you can't see.

 

If your ground is to a stud tack welded to the frame,find a nearby hole,knock the paint off and bolt it there.

 

Freightliner grounded to the frame if i remember right. That was always the spot we seemed to find the trouble was one ground studs on the frame.

 

We would run a 0 ga. Jumper from battery ground stud to starter ground studs on frame or run second 0 ga. cable from one of the batteries straight to ground stud on starter. Works wonders but even down here where we aren’t in your cold plugging in the block heater a little while before fire up if you are cranking on only 3 or less batteries helps a lot.

 

I'll just jump onto the pile of comments about bad ground connections too. LOL.