I have a 2000 Chevy astro rwd with a 4.3. It cranks but does not start. I have spark at all 6 cyl. I have 62 psi fuel pressure. I pulled the upper intake to ensure I didnt have a fuel leak from the injector spider. I get no codes. Replaced dist cap and rotor. Checked timing. pulled plugs and cleaned. What am I missing!!!??? I am about ready to give up.

Does your fuel pressure drop when cranking? How did you test for spark? I'm not 100% but I think if the Cam position sensor goes out on that motor, the fuel injectors won't fire. Do you have a scantool you can hook up? I also remember hearing that if the coolant temp sensor goes out, it will dump way too much fuel and likely not start.

I would start with what Jon mentioned.. unplug the coolant temp sensor and see what happens..

do you have fuel in the oil ?

Have someone crank the engine and you listen at the injectors. You should hear them fire, will be a click. If no click the injectors are not providing fuel. I'll have to check, but isn't that a VATs issue? So many different ways of handling VATs, some crank, some don't, some fire, and others don"t. I'll check some manuals.

The engine cranks but will not start and the Security lamp is flashing

Check your key, try a different key.

The crank sensor is also possible, but check the key first. Both can cause injectors to shut off.