Engine 'reconditioned' ignition issues

My 1998 A8 4.2l originally went into emergency shutdown mode while on a highway trip. With emergency dash icon showing, I pulled it off the road.

After tow to closes Audi dealer...they said it was 'probably' a skipped timing belt...damaged valves. Recommended an engine rebuild for about $4k.

Base on that info. & reading a lot of the posts on many Audi forums & audipages.com...I decided to give it a donor engine swap.

The original engine would still start & run for about 2 or 3 minutes before stalling out dead...I believe it was again a emergency shutdown by the computer.

My independent mechanic checked the original engine & found full compression on all pistons !!! No tapping, No raddles, No misfires...even after many months of idle time while I researched for information & assembly of reconditioning parts (timing belt, h2o pump, pulley's, oil coolant seals & pipe, valve cover gaskets, new cam seals...etc.).

Pulled the nose & rad for full open view & access. Found that the oil tooth pulley was very tardy... w/nearly frozen bearings. No broken belt, No missing teeth from the belt, a fatigued dampner/shock. When placing the locking bar on the cams...perfectly in TDC !!!

So w/full compression, cams in TDC & nearly frozen bearings on the oil pulley...we think that the oil pump pully issue caused low oil pressure issue. This could have been the reason for the emergency shutdown mode on the highway !!!

Replacing the oil pulley bearings, new TB, both cam seals pulleys, rollers & new dampner/shock for a trial engine start after slow hand rolling the engine a few cycles. Check the chamber compression again...ok But found two chambers were soaked w/engine oil !!! Probably leaking valve cover gaskets... The plugs has fuel (gas) smell....getting fuel delivered from the gas tank.

Tried to test start the exposed original engine... Slow crank.. no engine start/fire... the battery had a low charge.

Not sure why it wouldn't start...? So we are going to get a full battery charge overnight & give it a whirl again.

Any thoughts, suggestions &/or contributions would be greatly appreciated & helpful.