What is wrong if the car won't start? Also if the engine turns over?

Either its a bad new battery or tour altenator isn't charging it. Jumpstart it.

Your fuel pump is packed up and you should change you fuel filter as well its clogged

Check batry terminals are secure & free from corosion, check security of earth strap to engine & main power wire on starter, if ok have the batry load tested to ensure it can perform under load as the starter needs a lot of current. Have you tried a jump start?

-do you use the right key? (thick brown/black colored) after aou turn the key on, does a light go on on the dashboard?
- seems to be an issue with the lock code of the key (wrong key)
then the engine immobiliser does not allow to start..

I'd be happy to help you solve your problem, but you kind of sow confusion. So I ask, does the engine crank over at its normal starting speed when you try to start it? And despite the heading reference to the clutch slave cyliinder, the problem is the car won't start? I'll tell you where to start troubleshooting every problem with the car not firing up. That is to check the battery's present condition. If the battery is low on charge you cannot rely on any further testing. So have the battery charged up or check it with a voltmeter to see if it needs charging. Is your problem a one time problem, or any events leading up to this that may have effect? If the engine started and ran fine before, and you heard no noise of an abrupt failure, then it most likely lost either fuel or spark (ignition) to the cylinders.

Could be internal damage. Put a socket and wrench on the crankshaft pulley and see if engine is seized up. The thud is worrying, suspect major damage if the crank won't turn all the way round. If you can't turn the engine by hand, you will need a new engine (or new vehicle- that is a pretty old suburban, almost ancient to be needing a new engine!)
If engine still turns by hand, have your starter tested.

If the engine won't fire up, but your starter turns over, you may want to check your timing unless you have a check engine light on. If the CEL light is on, have the codes scanned.

If the engine won't turn over with the starter or it clicks, have your battery tested at autozone or advanced auto parts. Replace the battery if it is bad. Else, have your starter tested.

If the engine still won't turn over and the battery and starter are tested fine, you may have a blown fuse, bad ignition switch, or a failed relay.

If the engine fires up but randomly dies and starts back up, you either have a failed sensor, failing fuel pump, clogged fuel filter, bad plugs or wires, or a failing ECU.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

I've had trouble like that with my car before. Check the starter. A lot of times the starter can have the same symptoms as a battery. Hope this helps!

hi Bhuna.
this could be alot of things.
go to this link and see if it helps you out.
Why car won start troubleshooting tips

sounds like you have a good battery, get the car started put a voltmeter to wire connected to the back of your alternator. if you have at least 13.25 volts you have a good unit if any lower replace the alternator
the click sound you are hearing comes from your relay it is getting low voltage from the battery. because the battery has no juice caused by a bad alternator


hope to help shack