No crank with key, can jump and it will crank over, no Radio in RUN position, work fine in ASSy position. Engine will not spin over at all with key. Truck low miles like new, what gives? All fuses good and check a full 12volts on both sides. Any one had this happen before? Help???

 

more explaination needed.. You cant crank it, but it cranks when you jumper it ?? Are you jumping to the battery or the starter ? If your jumping to the battery, are you putting the negative cable on the motor/ frame or the battery terminal........ Sounds like your battery does not have a proper ground cable if your jumping around it and the motor cranks.

 

If you are talking about jumping to the starter motor and that works, then I would look toward the starter relay and see if it has a problem.. Does it CLICK" when you turn the key or not ? CLICK means your getting the 12 v signal from the key... If it clicks and don't turn, then the relay is not contacting internal. ......... If you have no 12 volt signal at the relay, then you lost the wire from the key switch to it.

 

It does click when you turn the key, I can jump the starter directly, not jump the battery. The key make no effort to spin starter, no power down to the starter when key turned to "Start Position" Radio will not play when in "RUN" but will in accessory position.
Truck was fine, low mileage 40,000 miles not driven much. No signs of a rat or mouse damage. Would like to find a diagram of the circuit so I can run down the issue. I do not believe the switch is the problem, but something else. Thanks for trying to get me going in the right direction. Thanks Again for all the help I can get.

 

look on the fire wall for the starter relay... It is the "CLICK" that you hear. The key is energizing the relay and pulling it in, but it sounds like the big contacts are not connecting to put power to the starter.. ... Have someone turn the key to start, and hear the click, check the 12 volt power lug (BIG) from the battery on the relay.. check if you have 12 v OUT on the other lug (BIG) when the relay clicks....... the OUT lug should go to the starter ?

 

Im not sure about the 2008 with the starter relay... the older than 2004 trucks have that... anyway, follow the big power cable from the starter up to the firewall or fender and you probably have a power block that it connects to... there should be another big cable that runs from that block to the battery. Your not getting battery power thru the relay to the starter cable.