I have a 91 S10 Blazer 4.3 Auto RWD.
Oil pressure had been running low at idol and high while driving. I noticed a VERY light surging at idol a couple days later I turn the key and hear a spinning noise like a gear not connecting, fast spinning sound no crank no start. A couple tries later it cranks over. Drives with no problem other than oil pressure fluctuating (figured it's a bad sensor since the temp stays good and drives great). Next couple start ups that day crank and start right away or on the 2nd try. I go in to get gas and then it won't start at all. Just a spinning sound. Dropped the starter and the flywheel teeth and starter teeth look normal. Tested the starter, no problem. Mechanic listened and said he was almost positive it is the timing chain. I just pulled the bolt ons, harmonic balancer, and tensioner cover thinking I'm going to see a hanging chain or broken teeth but it looks fine. The chain is loose but not broken. Does this mean it is not the reason for the no start? Engine is different than any I have found in videos. Such as no abs, carbureted, no nut on fan clutch, screw and lock nut flex lines, shimmed starter......
1st Chevy and 1st vehicle under 10k GVW.
​​​​​​Thanks

 

Im curious myself even though im 4 yrs late and mines a 2001 4.3 4x4

 

it could cause a no start if your timing chain is very loose in there, but i would also point the finger at your Dizzy. the shaft that goes down to the engine could also be worn out and give you a SES light or a no start. my previous Blazer "2001" had that issue with a SES light and sometimes back fired. found out later that the gears were very sharp and the timing was off because of the wear.

Have you done any service in your ignition system? like new cap, new rotor?

 

Loose timing chain that has not jumped a cog will not cause a no-start. Does the engine have compression? Stick your finger over a spark plug hole and crank it (careful if you have very tiny fingers!)