that's what I would do, but I'm not an engine swap expert.

 

I recently done an engine swap in my 04 Silverado from a 4.3 the the 5.3. I'm having problems getting it to fire up. I don't hear fuel pump kick on nor will it fire up if I spray starting fluid in the intake. my truck is not set up for flex fuel and I got a engine wiring harness from an flex fuel vehicle could that be my issue or is it something else?

 

Seems I read somewhere else this past week that if you do a swap like this that the computer is looking for an ethanol sensor that you don't have, and therefore prevents starting the engine.

 

Did you also swap the PCM or just the wiring harness?

 

PCM and wiring harness

 

Check fuel pressure with gauge and pull sparkplug wire to check for spark. Them are the first things I would check for no start.

 

Engine will start but won't start started. I have no electric to the cab or head and brake lights. My ignition switch is the only thing that works in the cab. Could it be the bcm?

 

Meaning it will start for a second or two and then stall? That’s the Passlock system doing its job.

How did you program the replacement PCM to the truck?

 

Didn't know anything about having to program the PCM. I've tried bypassing the security system but didn't work. Is the PCM same as ecm?

 

PCM = Powertrain Control Module - it’s a combination of an engine (ECM) and transmission (TCM). It’s what you have if there’s not a separate TCM.

The Passlock system is nearly impossible to bypass permanently. There is a workaround for installing a remote start but it still depends on the Passlock system being fully functional before the bypass can be utilized.

You swapped from a V6 to a V8 - using the PCM original to the truck isn’t an option - so the V8 PCM is not only going to have a different VIN and theft deterrent key programmed to it, but it may also have different power and ground inputs at the body to engine bay connections.

I’d recommend searching for mobile automotive programming services in your area. Even if they can’t complete the programming for whatever reason, they can provide you with more details on what exactly needs to be done to make the engine run.