question 1- if the timing chain broke would the truck turn over but not start and would it feel like there is no compression like the turn over is week, sounds very quiet. 2- if it is the timing chain how do i change it.
thanks guys

Probably not that - if the dist rotor is turning the cam is also and thats timing chain driven. Do you have spark? Do you have fuel pressure? Thats the two things to look at first then on from there.

I am going to try both mud thanks, hey how do i check the fuel preasure?

With a fuel pressure kit available at most auto parts stores.

http://i131.photobucket.com/albums/p288/Clunk_/Image026.jpg

Be careful, the Schrader Valve is right next to some sparkplug wires and the distributor cap. I stuff clean rags around the connection before turning on the keyswitch then still pay very close attention to the connection.

ok i took the dist cap off and the rotor is not moving when i crank the truck. Does this mean that it is the timing belt or could it be the dist.?

It can also be a roll pin in the dist gear sheared (if there is one like the older ones)

ok i took the dist cap off and the rotor is not moving when i crank the truck. Does this mean that it is the timing belt or could it be the dist.?

If engine if flooded bad from dist not turning or firing it will spin over free like low compression.
Pull the dist and check the dist gear and also roll pin as said.
I have saw a few eat up the dist gear.
Also check for dist shaft bushing wear when dist is out.
If worn out good time to replace dist.

If the distributor gear is intact, and the shaft is not damaged, you are likely looking at a broken timing chain (not a belt). It's not a lot of fun on a Blazer, but there are a lot worse. The accessories and the big die-cast mounting bracket are the biggest issues.