ok need lots of help. 1985 GMC Jimmy S15 (still a blazer) 2.8l v6 carb with auto tranny 4x4 and 168,*** miles.

ok i was driving the truck downshifted on the highway pulled over to slow lane it backfired twice pulled into breakdown lane and it died wouldnt start again.
-next morning it starts with some difficulty and has loping idle with the gas pedal pressed then dies and wont start again.

-i replace fuel pump and ignition coil for haha's nothing changes, i got fuel and checked spark to all places (6 cylinders and coil) and got it.

distributor shaft is solid and has no play i tried turning the dist. to try to get it started didnt affect it.

what is wron did it jump timing on the chain so bad that it wont start?
and did these trucks come factory with nylon cam gear for the timing chain and if they did could this be the prob. at 168,*** miles???
-how high of a possibility of it being bad compression is it?
please help i need my truck back
__________________________________________________ ____________
actually i might not be getting spark but i did a compression test and 5 out of 6 cylinders got 150psi and the last (back left cylinder) got 90-95psi

any suggestions?

 

Bad rings, bad valves, or bad headgasket... Pick your poison. Sounds like you need to do a leak down test and see where the air goes. That'll tell you what it is. If you hear air from the valve cover, it's likely the rings. From the exhaust or throttle body, it's most likely a valve (make sure that the cylinder is at TDC compression). Bubbles in the radiator, bad head gasket.

 

yeah but would that one cylinder have made the truck die all of a sudden and not alloow it to start again?

 

Shouldn't, but depends on what happened to that cylinder.

 

well me and my bud are gonna throw a timing light on it and crank it to see where the timing is at and if its off we are gonna pop the distributor put it to tdc and put the dist. back in then check again