I've noticed on my 1999 24v that the WTS light takes a while to come on.  All other lights have come on and off before the WTS light comes on. And there is no cranking the truck without that light coming on.

My 12v is not that way. 

WTS delayed start is a sure fire sign the ECM is dying.    The WTS coming on is the indicator for the ecm moving data into memory, IE booting up.

 

 

Test and clean ALL grounds.  Use die-electric grease on every plug under the hood.

 

 

And prep to replace your ecm.  

Test for excessive AC noise, and get ready for a new alternator as well. 

 

I'm experiencing the same thing, and need to get on the ball... I've been procrastinating.

No excessive a/c noise, however terminals at the batteries are not the ideal connections and need to be replaced. Hoping that's my problem.