i have replaced the starter and had the batt. tested. i have full power in side but when i turn the key to start, nothing happens. WTF!!!! this is a 98 gmc jimmy 2wd with a vortec 4.3

 

Have you checked all your ground connections to the battery and starter?

 

first thing i would do is stick a meter on the starter solenoid and turn the ignition on like you are going to start it (on the signal wire). If it has power then there is a problem down around the starter. If there is not power then it is on the other end ie: fuse, realy,ignition...

 

check your fusible links on the inside of the drivers side fender near the brake booster

 

I've gotten bad parts before...the starter might have you chasing ghosts. just a thought

 

I agree with the solenoid. turn the key on and touch a screw driver to the 2 bolts.. make sure its got a handle too, and if it doesnt spark is the solenoid, but if it does it should start if Im not mistaken

 

i had same problem and it was the ground that went to the engine block from the battery.

 

well... looks like every one posted my two ideas already haha... so I'm just posting to ***** up the thread.

but I do agree, you need to test the wires at the starter for proper current and check ground wires - either would be the most common issues found with those symptoms.

 

As mentioned, make sure that you're getting 12v to the starter solenoid. If not, check for a voltage drop along the starting circuit. Another idea that comes to mind is possibly a bad ignition switch.