Thanks for the rundown on what to do next. It rained for days and hard to get a helper with work schedules. I did give up trying to start it 6 yrs ago and it eventually seized while it sat so trying not to give up again. I used diesel to break it free then changed oil.

 

I bought a timing light and I'm beginning to notice something when light flashes when rolling over and timing mark is at 0 degree on timing tab mark the distributor cap looks way left to me. I will post some pictures

 

 

So I will fix that tomorrow and charge battery up good and do the vacum test again.

 

Here’s the cap layout and firing order for the 4.3




If the timing chain or distributor drive gear is off by only one tooth, rotating the distributor should compensate well enough to at least get it to fire and the actual change can take place once it’s confirmed. Which way you have to turn it depends on whether the timing is advanced or retarded (determined by the chain or distributor gear being off), so it will take some trial and error.

Make a reference mark on the base of the distributor where it seats into the manifold so you know where you’re starting, and can keep track of where you were.

 

Vacuum is an indication of how well the engine is internally sealed and can move air - it’s not excessively affected by ignition (spark) timing. Ignition timing that’s far enough off can cause minor needle fluctuations but it doesn’t affect the internal integrity of the engine.

Restrictions prevent air flow for obvious reasons - if you block off the intake, there’s no air getting in. If you block off the exhaust, there’s no air getting out which, in turn, prevents fresh air from coming in. Without air movement there’s no vacuum.

If the engine (specifically the combustion chamber) isn’t sealed well - stuck rings, hole in piston, valve timing being off, head gasket, etc - the engine can still move air but it’s ability to do so is depleted. This is indicated by low vacuum. The engine will usually still run but not very well - I once saw an engine that ran with about 9 in-Hg of vacuum at idle - about half the normal reading.

For me, vacuum testing is simply a method to determine whether the next step is to pursue a mechanical problem or an electrical one.

Good vacuum = electrical
Low/no vacuum = mechanical

 

So I did a compression test.
#1: 100
#2: 75
#3: 2
#4: 65
#5: 60
#6: 60

I tried adding 1tsp of oil squirted into hole #3 same reading and it will hold the 2psi so I doubt it's a leaky tester connection

 

Bright side being at least 1 cylinder has good compression?

Are you going to pull the engine or try to replace the rings with the block in the truck?

 

I figured it was a valve issue since the #3 cylinder didn't improve with oil or build any power each compression stroke so thanks for your wisdom. I would like to pull engine I'm not strong so whichever way is easier in end lol no cherry picker yet either

 

Is molly rings ok or better option?