I have 1996 chevy tahoe 350 vortec i have spark , fuel, and new throtle position sensor still only crank over no start though

did you have the passlock unit flashed to your vehicle

Hello. Yes, your Chevrolet's security system will 'shut-down' the ignition system; causing your truck to start but stop instantly. The truck 'thinks' it is being 'stolen' and will 'enable' it's security system to 'hamper' stealing it. Good luck and keep me informed; if you want to.

CKP sensor is located at front/lower of engine near crankshaft damper. Check for spark. Should blue with spark plug wire one half inch away from a good ground.

Loose battery cable at the starter end, or sensor trouble, tighten cables, see if this helps, usually does, I get 50.00 per hour to check this, I render this 4 free 2 u.
Thnx 4 using fixya.com

Maybe your timing belt broke. Have you checked that?

First check your fuses. Next, I would check my plugs and make sure they are not fouled and are gapped properly. I recommend AC Delco copper plugs in the Chevy 350 with a gap of .060 in. If the plugs are ok or that doesn't fix the issue, then I would test the fuel pump. You can do that by placing a fuel pressure tester in the line on the scrader valve at the driver's side firewall toward the back of the motor. Screw the tester into the test point, then turn the key to the run(not start) position, give it a few seconds and check what the pressure is. It should be 60-66 psi, if it is not you either have a clogged fuel filter(which is located in the frame rail under the driver's door) or a bad fuel pump.

i suggest removing the flywheel inspection cover, and rolling the engine over a little bit at a time, checking to make sure that there are no worn or broken teeth. also, make sure there is no lateral movement, which could indicate a broken flexplate. good luck.

is the distributer in correctly those only go in way only and there is no adjusting timing on those motors assuming it is the vortec motor

Mine did this with a cap and rotor. I changed it six months prior, but ended up having a faulty cap from Jegs which caused it to backfire. I had crank, spark, fuel, but the cap was crossfiring and wouldn't run.

This cost me a new flexplate, two starters, still a cap and rotor just due to the backfires.

replace your MAP sensor(manifold absolute pressure) the map sensor is the computer for your fuel pressure regulator telling how much pressure. Unless your tahoe runs like **** going up hill than it inevitably your fuel pump