ive been having trouble trying to start my 89 firebird i just recently did a 305 tbi to 350 tbi swap on it. before hand the car turned over and started fine but after the swap it wont turn over at all. the car gets good power, the starter is brand new along with the starter enable relay. i originally thought the problem was with the vats so i bypass that with the correct resistor to still have no luck however i do still feel its vats related. the security light comes on and goes out after a few seconds as it should but when you go to start it the starter relay just clicks. the wireing harness and ecm are still the original pieces and all sensors are hooked up as they should be. if anyone has had a similar problem any help would be great this is starting to drive me crazy cause i just want to get my car running

 

check your ground wires.

 

ground wires are fine that was the first thing i checked

 

The start signal goes from the start enable relay to the neutral safety switch ( auto trans) or the clutch interlock switch (man trans). Its a dark green/wht wire. The neutral safety sw is in the console on the shift lever bracket, the clutch sw is on the clutch pedal bracket. The circuit from either switch to the starter is a purple wire. You need to check whichever switch you have to be sure its closing. You can jump the switch for a quick test using a paper clip. I assume that youre hearing the sart enable relay cick which only leaves the n/s sw, clutch sw, or the sarter solenoid. If its the starter solenoid youre hearing click then you either have a bad starter or a bad power supply or ground. Visually checking the power and grounds is only a start.

If the starter is clicking, you need to test power at the starter while trying to crank the engine. Wires can break internally and you wont see it. You want to test for an excessive volt drop across either the power wire from the batt to the starter or the ground wire from the batt to the block. You need a good volt meter and a helper. Hold the red test lead at one end of the wire and the black lead at the other end. Watch for a voltage reading while a helper tries to start the car. Any voltage you see in this test is volt drop in that wire. More than 1 volt in either wire is excessive. Be sure to double check batt terminals and connections at the starter and block.
Hope this helps.