no obvious reason the motor would fail on a 30min drive, given you have been driving it anyway

 

It's a pretty simple test with a multimeter to see if the driver in the ECM is shorted through and holding the injector open. Just measure the voltage across the injector connector with the key-on. Ask the mechanic to check it real quick if you're concerned the ECU is bad. If the ECU was holding the injector open, it could have overheated your replacement too.

 

That's still a horse-crap diagnosis in my book. You didn't get any more answers. Why *Exactly* is there no compression? What is the specific reason? (bent valve, hole in piston, etc)? Even if there's a big hole in the piston, a mechanic could possibly stick a new piston there in an afternoon at a fraction of the cost of a new motor ... (provided the cylinder is not scored) and possibly get many more miles out of it.

Even if it were something rather severe, the head needs to come off and answers need to be given so you know what direction to go. You should fire that mechanic too and keep looking.

But to answer your question, you should be able to drive it to the engine replacement guy. Try to keep it low speed. Before he digs deep into buying a replacement engine, and before you commit on any replacement engine, have HIM pull off the head and give you a better diagnosis and what he thinks the best way to go is. You never know.

 

I'm very curious to know the cause myself, and would at least stick a boroscope in there and pull the valve cover. Since he's paying a mechanic though, the labor cost to repair it could easily exceed the cost to drop in a good used motor. Depending on the damage, he might end up pulling the motor to repair or replace anyway. I was planning to rebuilt he motor in my MJ, but found a motor for $300 that had been rebuilt 25k miles earlier. I couldn't even buy the parts to rebuild mine for that.