Awesome, thanks for confirming that. It looks like it should work just fine wired up like that. So if the hydraulic fan solenoid operates at 100% without the "engine coolant temp" / PWM signal, the PCM is essentially cutting power to the solenoid with the PWM signal in increments. That's how it knows when that circuit is disconnected or malfunctioning, if it doesn't see voltage on that circuit? So in theory you could satisfy the PCM by just connecting the two wires on the hydraulic fan solenoid? Or better yet in my case put that signal to proper use with the electronic fan relay. Good stuff.
So having deemed the engine cooling roadblock out of the way, I bought the radiator and mechanical fan / pulley from the 99 4.7 WJ at the junkyard today. The only other thing to straighten out with the swap now is power steering since there doesn't seem to be an easy and reliable fix for using the 4.7 pump with the hydraulic fan eliminated. Since the pre-01 P/S pumps are the same for both engines, I should be able to bolt up my pump, although it may need a different bracket, I'm not sure yet. Absolute worst case I will have access welding equipment at my uncles shop and can modify / fab a new bracket if it comes to that.
Everything else seems like it is a go. Looks like the connection to the fuel rail is the same and in essentially the same location on both engines. I decided to add the entire exhaust system to the swap list while we're at it. Other than being newer, the reason being our Jeep is CA emissions, so it doesn't have an O2 sensor bung after the main cat. After studying the 99 4.7 WJ in the junkyard today, everything is identical under the hood, like the EVAP system. The 04 is a bit different so we'll see what if anything I decide to update.
Looks like I've thoroughly analyzed this through... hopefully the auction for the donor car I'm after on Monday stays within my budget and I can win it. Since the front end and interior are pretty much beyond feasible repair it shouldn't get much if any attention. Even if I don't win this one, I'll find another soon. Then nothing to it but to do it!
Last edited by CopperDeer; 07-18-2013 at 08:53 PM.