New here and couldn’t find anything through searching the forums. I have a 2011 Yukon 5.3 that I replaced the cam, lifters, oil pump, and timing chain. I did not do the AFM delete and went back stock, once all
back together I cannot get it to start, it barely turns over almost like a timing issue. The battery is new and fully charged and the starter was swapped for a known good one. When it sits for a while and I try to start it it seems like for a split second that it wants to fire up but then struggles to turn over. I pulled the timing cover back off and timing is spot on, I’d love if anyone could try some ideas my way. TIA

 

Turing over slow when battery is good and starter is confirmed to be good is typically a grounding issue. The block must be properly grounded with a big ground cable, in order for the starter to work properly. It’s a high amperage motor and requires a big ground cable. Check your grounds to block/heads.

 

Put the negative batt cable on the block somewhere; or, as close as possible. A head, a bracket, something that's a solid part of THE ENGINE, solidly bolted to THE BLOCK.

DO NOT hallucinate that the neg batt cable can go to the chassis somewhere, ANYWHERE. That will result in negligible starter performance EVERY TIME, unless there's a BATTERY CABLE SIZED piece of wire bolted to THAT PIECE of the chassis and going straight to the block. And even then, it's still INFERIOR to doing it right.

Put the copper where the current is; NOT what "looks" "good", NOT "what's easy", NOT anything else. The single highest current path in the ground system is between the batt and the block, carrying starter motor current. (expect a couple hundred amps) Next highest is alt to block which of course is usually taken care of adequately by merely mounting the alt. EVERYTHING ELSE on the ground side of the electrical system is secondary to those 2 paths.

Once you have the batt cables properly connected, you should of course make sure that the chassis is securely connected to the block; that's what the factory braid straps are for. You can duplicate those, or upgrade them with larger wire, or whatever; butt get the priorities straight FIRST. Batt to block, then everything else afterwards.

 

Volt drop tests are in order.

 

How east does it turn over by hand? No binding?

 

Use some jumper cables to ground the block better for a quick test.

 

Good call here. Dawson, pull the spark plugs and see how easy the engine turns over with a breaker bar on the crank bolt. You might be seeing negative camshaft endplay if you didn’t check that when you put it together.
So to recap here, you put NON-DOD lifters and camshaft in the engine but you did not replace the DOD valley cover? Has DOD (AFM) been turned off in the tune?