When i turn the key on my 99 tiburon nothing happens.

Yes, it has to do with the ignition switch. but just as possible could be a battery connection from the battery to the switch. So, sometimes turning key to ON causes no dash lights or warning lights to come on?
That sounds like a bad switch, or more likely, a bad battery connection or a bad connection between the battery and the switch. First thing to do is check the charge of the battery, it must register at least 12 volts. 12.6 volts is the ideal for a good and fully charged battery. Clean and tighten all battery connections.

Sometimes when you have a poor connection, from looseness to corrosion, and you turn key and see all warning lights and gauges come on, and then turn key to start and everything goes black...that can happen because the power surge causes the bad connection to come apart. So check for loose or corroded connections.

You may have a dead cell in the battery , or damp in the electrics.

check connection and wires at battery for damage or corrosion if good check for power to ignition switch if no power check for damaged or shorted wiring if good turn key and check if power going to relays or accessory's at fuse panel if no power switch may be bad

If the engine will not crank, you could have a problem with the key switch, the neutral safety switch, the starter, or a cable connection.

fuses - including the eingine fuse itself,. otherwise you may want to tap on the starter while someone trys to turn it over,. otherwise remove, test (if good) replace starter) was the starter solenoid replaced with the starter? are all the connections including the battery ground cleaned/ inspected? You may have a bad starter or bad solenoid, even new (rebuilt) that can happen..
best regards
Ck

Hello Kimberly 210,

I looked up your ignition to assure MYSELF your
key ... is indeed a standard TRANSPONDER.
(no idea what country we are talking about...??)

That type of response SEEMS to be a SECURITY
response... As though ONE of your keys is in trouble...

(TRANSPONDER KEYS can be damaged & intermittent) ...

My best advice is to get on eBay and find yourself
a COUPLE of NEW uncut OEM key replacements...

Shop around and find out if you have a cooperating
locksmith who will cut and code the keys for you...

The BEST price I've paid was $6 per key cut...
The worst was $60..
(they ruined my OEM key and sold me a generic
(I felt it was deliberate.. my OPINION)).

IN ANY CASE: If you wait until the key goes bad a DEALER CAN GET (page 120, 3-10 owners manual)
from $300 to $600 for full key service AND that
IS NOT INCLUDING the tow charges.

Some cars allow you (the owner (nothing found))
to code the keys yourself...

but you CANNOT do it WITHOUT at least TWO (2)
WORKING KEYS...

Sorry... I don't know TIBURON specifics

http://www.rockauto.com/en/catalog/hyundai,2003,tiburon,2.7l+v6,1415876,ignition,ignition+lock+cylinder,10041

More Information for STANDARD MOTOR PRODUCTS US673L

HYUNDAI TIBURON 2001 2008 GENUINE BRAND NEW BLANK TRANSPONDER KEY...

Owner manual (same site has WORKSHOP MANUAL)
Hyundai 2003 Tiburon Owner Manual

clean battery post, check battery to srr if it will take a charge tighten cables to battery

The problem may not be either. The first thing to do is to make sure your battery is fully charged, if the battery is fully charged then you have either a bad connection or a bad starter.
If the battery is not fully charged the next thing to do is to get the battery fully charged and have it load tested to see if you have a bad battery. Most auto parts stores will do this test for free.
If the battery checks out then your problem is most likely the alternator but before you just replace it have it tested too. You could still be looking a just a bad connection.
One thing that often gets over looked is a weak or bad grounding connection.

need new battery the click you hear is lo voltage from the battery or at least have it fully charged then load tested at local parts store

hope2help shack

Possibly the alarm cut-off switch? or Ignition key switch (or wires) going bad?

But you mentioned you tried to jump start it and it did turn over?
IF so, you could have severe corrosion or loose connections of the battery cable both at the battery and at the termination points, such as ground and starter motor.
Check that the battery wires are tight and clean at the battery posts and at the other end.

Again the No lights suggests either the alarm cut-off, or an absolute disconnected battery cable.

Finally, it could be ignition fuse, Check fuses. Ignition key switch.

What makes this hard is that you suggest it would turn over with another battery connected. This makes no sense.

Good luck