Still sounds like a battery connection problem. Get new battery cables and clean the ground contact point as well.

Check the fuse (main one) I think 140 amp where the power comes in the PDC.

 

I'll recheck all that again. I replaced the battery cables about a year ago, but I'll recheck them to make sure they haven't loosened up somewhere. The connections at the battery still look like new.
Here's another wrinkle that may or may not have anything to do with this. I have a Viper alarm. About 3-4 months ago it started acting up. It has a remote start. It starts the truck fine, but when I use the remote start, pressing the brake is supposed to cancel the remote start. Pressing the brake no longer cancels the remote start. I have to cancel it with the key fob.
The strange thing about this is that the truck will usually start and run just fine. After I installed the new alternator and battery, I drove it for a week to make sure it was all good.

Thanks again for the advice. I'll post what I find as soon as I can.

Jack

 

Could be your alarm is fritzing out on you. Do you have a warranty for it? Maybe have them replace it.

 

definitely check into the alarm functioning correctly, aftermarket alarms can cause all kinds of problems if they malfunction or are installed sloppily

 

The alarm system!

 

Finally got a chance to work on this again. Pulled the alarm out from under the dash and there were 4 wires pulled loose. One was the power - reconnected that, and the alarm started working again. I don't know where the other 3 go. They are orange, brown, and black/white. This is a Viper 479V with remote start. I found one simple drawing that showed the black/white was the neutral shutdown circuit. The alarm thinks it's in gear, and won't let the truck start.
I would just take the truck in, and let BestBuy fix it, but it won't run.
Any ideas? Anyone?

 

check the viper alarm website, they should have a pdf installation manual with wiring diagrams for it

EDIT: you sure thats the right number?? bc i cant find anything on the 479v it goes 460 then 480

 

I did find an installation manual. Viper won't give it to anyone but installers, but I was able to find one anywan. And you're right. It's a 791XV.

I have everything connected now but the neutral lockout. I found another website that lists that wire, but I can't find it. It's supposed to be a yellow wire on the left side of the steering column.

Still looking...

 

Time to go back to basics. I talked to my alarm guy. He said putting the alarm into valet mode, or removing the fuses that control the alarm system would take the alarm out of the equation. I did both, and still no start.
I pulled a spark plug to check for spark (which I should have done a long time ago) and it was wet with fuel - no spark. I think my problem lies elsewhere.
Still looking for an answer.
Jack

 

Remove the alarm.