No fuel no spark 1990 k5 blazer 350

My first suspect is a clogged fuel filter.Also, check spark plug gap. It is possible the gap is almost to great and when heated up expands and the electric arc fails.

you need to make sure your spark plugs are in the right firing order!

Have you checked Google I found this hopefully it's not your timing or it may be flooded but doubtful have you tried spraying starting fluid into the intake while cranking it

Is the battery now flat again? Has the alternator drive belt broken? Has the alternator output been checked?

Note that if the new battery has been totally discharged by a lack of alternator charging then it's probably ruined and may need another replacement.

The temperature sensor is where I would start. If the sensor tell the computer that the engine is cold it will initiate the warm up mode which includes advancing the timing along with a rich fuel mixture. Unfortunately, there are many sensors that assist in controlling timing and fuel mixtures that it is difficult for me to give you a guaranteed solution.

If you are set on using this engine for its increased power and fuel efficiency, the only way you will realize these benefits is by changing the ECM/PCM from the engine donor vehicle to yours, put the 90 model engine's throttle body back on it, use the engine wire harness from the donor vehicle--in other words, the engine has to think it's still in the Caprice, and the only way to do this is to put the Caprice electronics and fuel management system (throttle body) back on it. If you have to modify the throttle linkage, the kick-down/TV cable, to make it work, then do it. Also, you will have to put an Oxygen sensor from a 90 Caprice into the manifold/collector/crossover pipe of your vehicle, and not one for the 87 truck. If it wont fit, plug the factory hole on your truck's Oxygen sensor location with a threaded plug using high-temp thread sealant, cut/weld in a proper-threaded orifice for the Oxygen sensor from a 90 Caprice. If the Caprice had two Oxygen sensors, you will have to put one on each cyclinder bank's exhaust outputs.
Swaps such as these are great if all the details are attended to, but headaches if you just try to throw and go.
If you do all this, the codes will not come back after you reset them, the engine will run great, you will have better power and greater fuel economy (the Caprice and the Blazer weigh within a couple hundred pounds of each other), and you will have a 1987 K5 Blazer which "thinks" it's a 1990 Caprice.
And remember when buying engine parts in the future to tell the counter guy "It's for my other car--the 1990 Caprice."
You get less **** out them that way.

CHECK FUSE + RELAY TO FUEL PUMP.IF THEY CHECK OUT GOOD.YOU HAVE PCM PROBLEMS. MAKE SURE PCM FUSE IS GOOD.YOU CAN BUY A HAYNES REPAIR MANUAL.IT HAS ALL OF YOUR ELECTRICAL DIAGRAMS.

The most likely cause is water allowing secondary (spark) voltage to go to ground. Look at all plug wires. Inspect carefully the inside and outside of the distributer cap...

There may be no injector pulse if the computor does not see a RPM signal.
There will be no spark if the ignition module does not see a dist pulse from the dist pickup.......a RPM signal.
Because you do not have both ......I would suggest to check/change the dist pick up.
Follow the wires from the ignition module inside the dist to the pickup which is also inside the dist.
If it is just a bad dist pickup....keep all your old parts as good spares.
Also...is the dist turning? to provide a RPM signal?
You will have to remove the dist to change the pick-up.....mark your timing locations......"rotor position" and "dist body location"before removal.
A quick test before installing the "repaired dist" .....plug it in the the truck wiring and turn on the key....DO NOT CRANK THE ENGINE OR YOU WILL LOSE YOUR DIST ROTOR CORRECT POSITION......as you spin the dist by hand .....the injectors should spray.

fuel pressure isnt right.. need to get a fuel pressure regulator so you can regulate the gas flow..