Just pulled my 4.8 and swapped it for a 5.3. I checked all the plugs and connectors and they all appear to be plugged in. Am getting fuel and spark, tested those already. Timing is also correct.

I only counted a couple grounds total but I am thinking I may have missed one, or have one connected in the wrong spot -
1st ground goes from the back of the engine to the firewall
2nd ground is in the intake manifold wire harness (where should this go?)
and then the negative battery cable to the block (i have it connected to the block where the power steering bolts to on the side. Is this right?)

Any ideas? I am still running off the 4.8 ecu but will tune it with HP Tuners once it starts.

 

Not positive but I think you need to reflash the computer...or use one for a 5.3..

 

k. I will try reflashing mine with HP Tuners. I did read that the 4.8 would start it. I am also researching now - I read the VATS could cause a similar problem but I read I could disable it in my tune to eliminate it. Not sure if anyone has experience with that ?

 

Hopefully someone else will chime in...but that's what I'm thinking...but I could be wrong..

 

Thanks. I will give it a shot tomorrow after work. I forgot to mention - I did replace all the sensors on the 5.3 engine before putting it in. So the cam and crank sensors are both brand new.

 

Try disabling Vats in your tune first and see if it will start.

If it does then that was the issue. If not then try flashing in a 5.3 tune in.

 

A 4.8 pcm will start a 5.3 engine and run .

 

So are you saying this isn't hooked up? If so it goes to the back topside of passenger side of the block. Bolt goes in from top into block. Here's a pic maybe that'll help



I ALSO WIRE WHEELED ALL THE GROUNDING SPOTS JUST SO THERE WOULDN'T BE ANY ISSUES.

This might or might not be your problem but I'd double check all the grounds first.

 

Ahhh so thats where that ground is supposed to go. I got it bolted to the back of the block, not to the top like you have pictured. I will change that and then try disabling the VATS. Would it need to do a crank relearn because of the new crank sensor, or should it still start without the relearn ?

 

As long as its grounded I don't see it being an issue. I just grounded it in the same spot as the stock 5.3 was when I swapped the engines. Good luck man!