99 gmc jimmy wont crank..replaced battry..still no sound or turnover..how do know where to go next..starter.?..cylenoid.?..or fuse..

Try the light test.
1. Turn the lights on. The head lights should burn brightly.
2. Wiggle the battery cables and see if the brightness of the light changes.
If it does, then check the cables for looseness and tighten as needed.
If it doesn't, then go to step 3.
3. Turn the key to the start position and observe the lights.
Do they continue to burn brightly with no change.
Do they dim down considerably but, remain lit.
Do they go out completely.
If the lights do nothing and continue to burn brightly, then the problem is between the ignition switch and the starter. Check any fuse that has "IGN" in its description. If the fuses are OK, then you could have a bad ignition switch or a bad starter solenoid. Usually when a solenoid goes bad, you hear some kind of noise like a clicking sound. If you hear nothing at all, then check engine and body grounds before doing any thing else.
If the lights dim down but remain on, then the most likely cause is something mechanical like a bad starter or a blown head gasket. If you remove the starter yourself, then you can take it to a parts store and have it tested. There is usually no charge for this service . If the starter checks out OK, then remove the spark plugs and try to start the engine. (disable the ignition system by disconnecting power to the ignition module). If fluid comes out of one or more of the cylinders, then a blown head gasket is indicated.
If the lights go out completely, then the most likely cause is bad battery cables or bad starter solenoid if the battery is new. The cables can be checked with a set of jumper cables. The solenoid can be checked by placing a jumper lead between the large and small terminals of the solenoid and see if the starter works. If it does, then see if you can locate a fusible link in the wiring harness and repair as needed. If you need any additional information, then post a comment and I will get back to you as soon as I can. I hope this information is helpful and thank you for trying Fixya.com.

Ok if you have a test light hook your test light to a good ground use the probe and touch terminal on the starter with the pruple wire attached to it and have someone turn t he key to the start position if your test light lights up and the starter does not turn then you have a bad starter, If your test light does not light up then you have a bad fuse and/or bad relay! good luck