Here's a little back history, I bought this 97 4x4 to use as transportation on an island for $500. It has a 4.2 and had a knock when I bought it. I read that the 97s were bad about hydrolocking and this is what it seamed to be. I found another 4.2 out of a van for $500 at a local yard. It was my understanding that it was a direct replacement. I finally got the motors swapped but the "new" motor will not start. I did have to swap the wiring harnesses so that the connecters would connect. There is definitely spark at the ignition module. There is an occasional pop here and there when cranking the motor, I even tried using starting fluid but still will not fire. I hooked up my code reader but it did not pick up any codes. I don't want to put too much into this truck because it's going to rust away on the island anyways from the salt water. I can't afford to lose anymore hair so I'm asking if anyone has any ideas what I could be missing. I tried to include everything I did or tried. Thanks for your help.

 

There is not enough information to even guess.
I can tell you however that if the motor cannot run you won't have any codes set because there was nothing for the PCM to detect if it does not run.
First thing, is the fuel pump running at key, on for a few seconds?
Is there any fuel pressure in the fuel rail after several ignition 'on' cycles?
Is the crank sensor plugged up?
Is the cam sensor set in correctly?
Are the plug wires on the correct cylinders?
Is the coolant sensor connected?
Cold start uses a specific strategy of rich fuel, open IAC and advanced ignition timing set by the computer from what it sees at key on from the coolant sensor and the intake air sensor.
I know it's all elementary but we can't tell from here.
For a swap like this, if I could tell you exactly what was wrong, I would be a pretty good remote diagnostics god, I am not.
At this point even a Scanner won't tell you much of anything because it has no data to look at.
I would try to retrofit the new motor as the old one was because you don't know what all the differences are.
This would not be much different than replacing a short block and using all the original outside equipment so it all plugs up to the original harness..
As it is now you have to contend with the swap hassle plus any faults present.
You gotta be good to sort them out.
Good luck.

 

I would agree with bluegrass, retro fit the old wiring harness to accommodate the new motor, don't try to accommodate the vehicle to the new motor. the harness from the new may not send the same signal to the same sensor. try to use same harness from your vehicle, not from the new one. good luck