Overheated engine with belt off but still ran rough when shut down. About 1 gallon fluid steamed out. Engine turns over but no spark. Fuel pump operates. Engine code 12 showing. Coil is good and so is distributor to SBEC voltages at the connector.

with a compression of 150 psi the timing belt will be in the right place so that can be eliminated . you need 3 things to make an engine run they are compression ( which you have plenty of --- fuel you can hear the pump but are you getting pressure in the fuel manifold and lastly spark. So have a pressure test done on the fuel manifold top check for pressure regulator --pump/ filter faults . Next check for spark at a plug lead. Check that the injectors are working . Missing just 1 of the 3 will not run an engine.

Well, you over heated it if you saw steam coming out. If you warped the head then you may be sucking air or throwing water into the pistons causing a no start. 1st is to make sure you are NOT putting water into the bottle or radiator. You need to be using coolant (Anti-freeze) 2nd, check to make sure you're getting gas 3rd make sure you're getting spark. If all is good then I would remove the spark plugs, and let them dry off because they're probably loaded with gas. Cut the fuel pump from pumping gas into the cylinders by either pressing 1/2 way down or all the way down on the gas pedal. Crank engine over 5 or 6 times to blow the gas out of the cylinders. Replace the dried off plugs or put new ones in. Turn key to on position count to 5 and start car. if that doesn't work try a 1 second squirt of starting fluid into the breather. If it starts great, if not then you probably need to look at the cam or crank sensor.

The only way to know for sure is to hook a gauge to the rail and check the fuel pressure when it won't start.
Sitting for a few minutes and restarting is normally a sign of a relay or coil cooling off.
There should be a EEC relay that powers the dist module and ECM.
I know you said you have spark, but it could be something else
related.
Also, if you have spark at the right time and no fuel pressure, you should be able to use starting fluid to substitute.
I don't suppose you have dual tanks and the switching valve is the problem ?

No crank to a mechanic means the starter motor doesn't spin the engine over, is this what you mean? Or do you mean the engine cranks over but will not fire up and run? If it is the latter have you added at least 3 gallons of gas to the tank to make sure the electric fuel pump inside the tank can properly prime? If not do that, also you can spray starting fluid into the engine engine air intake pipe after adding the 3 gallons and see if that gets it going. If it still will not start you have burned up the fuel pump and you will need to drop the fuel tank and replace the pump, remember the pump is cooled and lubricated by the gasoline it runs in, so when you run low on fuel or out you can very quickly severely damage the small electric fuel pump. Never let the gas gauge level go below 1/8 tank to prevent premature fuel pump failure.

SOUND LIKE PROBLEM IN WATER PUMP AND TIMING BELT.WATER PUMP COULD HAVE LOCKED UP THROWED OFF TIMING.CHECK SEE IF COOLANT LEAKING OUT OF WATER PUMP WEEP HOLE. IF SO REPLACE WATER PUMP AND REPLACE TIMING BELT ALSO BECAUSE TIMING BELT AND COVER HAS TO BE REMOVE IF YOU REPLACING WATER PUMP.

nope! fuel pump sounds right replace it

take the head off bent valves thats for sure

if you dont have test equipment then you can determine what is likely wrong by the followint:
spray a little starting fluid or gas in the air intake (without the air filter) ... if it starts and runs for a few seconds then the ignition system and timing belt are likely ok .. you should then check the fuel pump and fuel filter ( a mechanic would test for fuel flow and pressure) .. you could have a blown fuel pump fuse ..if your car starts after spraying the starting fluid and continues to run but very rough .. then you might have water in the gas (more common as weather changes cause condensation). ... if the car doesnt start even with the starting fluid then you likely have an ignition problem .. you can remove an ignitiion wire and test for spark as the engine turns over ... if there is no spark then you could have a bad ignition module, coil or other ignition component.. if your lasabre has lots of miles on it you might check to see if it has a timing belt vs a timig chain .. the bels have a limited life time and can break or skip a tooth ... if it startted and ran a few seconds with the starting fluid then the belt is not the cause.. .

Check to see if you have a fuel pump shut off switch on the drivers side compartment. They do tend to trip. It is not good to run dry because the system will have to pump all the fuel through the entire system again. Do you have engine codes or is your check engine light on? If it is, I would have that checked out first thing.
If not, check fuel pressure, check for spark and so on.

The most likely senario is that the water pump went bad which caused the overheating in the first place. Then after the engine shut down, the water pump seized up. When the engine was restarted, the timing belt started to smoke because the water pump, which runs off the timing belt, was not turning. Since the engine overheated to the point of shutting down, blown head gaskets are a possibility. Put a new timing belt and water pump on it and start it up. If it runs OK, you're good to go.