98 Blazer will not start. No fuel pressure, no spark, but cranks over. Security light comes on after cranking. Re-learn procedure did not work. Next step I am taking is a new key cylinder as it has a magnetic trigger that "wears out" according to a retired GM mechanic. How do i code my old key to work in the new cylinder? If this does not work what else should I check? Please note that this vehicle does not have resistors in the key.

use your key fob to start it,your security is on

How do you know it's getting gas ? check fuel pressure . Are the injectors firing ? Spray some carb. cleaner into the engine , through the throttle plate , to see if it starts . Any lights lit on the instrument cluster ? SECURITY ?

Kelly, could be a few issues, security lock out, crank sensor, fuel pump fuse/relay, faulty new pump,faulty ignition switch, etc. Attached links may help you diagnose the crank no start issue you are having.
Check the attached links,video,instruction and guides, Good luck
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I don't think the anti-theft is the problem.
On GM vehicles, the anti-theft system will not allow the engine to crank, or get fuel or spark. If it cranks, you have a different problem.

You say it has fuel pressure, if it has sequential fuel injection it needs about 70psi to start the engine.
If it cranks and has spark to the plugs, the anti-theft system is not involved.
You did not mention the rotor, I assume you have spark to the plugs not just out of the coil.
If you have not yet checked cranking fuel pressure, I would start there. The pump could be weak or the filter stopped up.

TRY THIS PROCEDURE WITH IGNITION ON WITH KEY IN SWITCH.LEAVE SWITCH ON POSITION WITH ENGINE OFF. FOR TEN MINUTES WATCH THE SECURITY LIGHT IF IT TURNS OFF IN TEN MINUTES.TURN OFF IGNITION SWITCH FOR 5 SECONDS THEN TRY STARTING DO THIS PROCEDURE TWICE.IF CAR DONT CRANK THE DEALERSHIP HAS TO REPROGRAM NEW KEY AND IGNITION SWITCH.

before u change anything else,,,,put a scanner on it ,,snap on,, mac ,,metco,,& while cranking it reed the variables in each , to even see if their work in ,,or get a spark tester,,their cheep,,plug it in,,turn motor over,,if no spark,,could be pickup coil,,cam,,or crank censer,,hoped it helped

ecm more likely

Non-start situations basically boil down to two things: No Fuel, or no spark.

I you are looking to throw a part at it, start with the crank sensor. They are cheap and not too hard to replace.

A full diagnostic approach would be to determine if it was a fuel or a spark problem. Check fuel pressures with a fuel pressure test guage: Low fuel pressure indicates a bad fuel pump or a bad fuel presssure regulator. Lastly on the fuel side, check t see if the injectors are getting a signal to fire, usually done with something called a noid light, I believe.

Spark diagnosis begins with first determining the condition, then finding the cause. Bad coil, loose wires, even the crank sensor are all suspect. A good repair manual with a flow chart is probably the best procedure to follow.

In my case, my manual only had a passing reference to the crank sensor and no diagnostic procedure to test it or even lead me to it. I found the solution through extensive web searches. Once I replaced it, all was well.

I would say the car is not getting any fuel. you could try replacing the fuel filter which is cheap. It could also be the fuel pump which is probably in the tank.(try tapping the gas tank with a hammer lightly) If the car starts then it is probably the pump. The last thing i think it could be is that is isn't getting any spark. Take the spark plug wire off the plug itself and put a screwdriver in the hole and make sure it is touching the metal part of the plug. Have someone try to start the car and hold the screwdriver near a piece of metal, if you see a blue spark then the car is getting spark, if you see nothing then you probably have a bad coil.