5.7 Vortec intermittent long crank --> crank no start, backfires, clunking

[slow_c1500]

How long should I (or the other person) have to crank it to see a spark? I don’t want to crank it unnecessarily long

 

[99xcss4]

I heard it can be hard on them to crank with distributor wires unplugged.

I have never heard that before not saying it is wrong but people have been doing this a long now and not having any problems

 

[Keeper]

So it starts fine when everything is either hot or cold, but hard starts while it's cooling down.

Disproportionate cooling item? something external is cooling down faster than the engine itself and losing proper signal/connection during that time?

crank position sensor? starter solenoid issue? battery cables/connections? just spitballin'

 

[99xcss4]

How long should I (or the other person) have to crank it to see a spark? I don’t want to crank it unnecessarily long

5 seconds or so should be enough then stop and try again to confirm

 

[slow_c1500]

Good news, ignition coil does spark. So does that mean that the rest of the ignition system is fine, just the spark isn’t getting to the plugs? Or could it still be a cam/crank sensor?

 

[99xcss4]

I do not know about the sensors but maybe a new cap and rotor maybe a set of plug wires might fix you up at least your coil and ignition module is good

 

[99xcss4]

if you do not have one of these or know some one that has one of these I would get one easy safer way to check for spark at spark plugs https://www.ebay.com/itm/3742231510...Y/njyQhmD8adzETaTWvZNCQh4m|tkp:Bk9SR9rFmdD1Yw

 

[slow_c1500]

I should mention that when I did that test, the coil wire was plugged into the cap and not the ignition coil. Because of this, I wanna say the cap and rotor are good for now. Should I repeat this test with it plugged in oppositely?

It has to be something that, if it went bad, would make all 8 cylinders lose spark. Plug wires are good, ac delco, replaced them about a year ago. It can’t be spark plugs cause they wouldn’t all 8 suddenly die at the same time with zero previous misfires to warn me.

 

[99xcss4]

this is what I do I check to see if the coil is sending spark to the cap then I check to see if the spark is getting to the spark plugs from what you are saying it sounds like you are getting spark to the plugs what you need to find out is if you have continous spark or intermintant spark when you checked the spark was it a bright white/blue or a dul yelow orange if it is dul/dim that is weak spark when you get started again I would look at live data if your scan tool can do that might help

 

[slow_c1500]

It was a blue spark, and yes the coil is sending spark thru the wire as well.