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.

[Conan_the_Librarian]

Interesting set of symptoms. I'll point our resident expert in the direction of this post for his opinion.

Any quick guidelines for compression psi? I'm awaiting my Bentley repair manual (dvd)...anyone have a quick review available?

I believe the 1998 Audi A8 4.2 L (ABZ) has 10.8 to 1 ratio. The parts counter person @ one of my available Audi dealers obtain this for me this morning but because of time & 'running back' to personally speak w/his buddy tech...he did not think to get the PSI reading and/or variances levels as I originally ask him to seek....

Any thoughts of high or low compression ...outside the called for standard?....your experiences?

I did not read any posts or threads w/very much details related to psi compression reading...then possible cause ...thus probable solutiions !!!

Re-checking the fuel supply, compression values w/gauge and electrical 'spark'. We are also awaiting for the 'full boat' Ross-Tech scanner. My 'skinny' version will not provide enough information in all of the modules & ECU.

Still digging !!!

Thanks again for any help, suggestions & thoughts.

[ainarssems]

ABZ engine Compression ratio 10.8, Compression pressure new- 10-15 bar (145-217 PSI) wear limit 7.5 bar(108 PSI) maximum permissible difference between cylinders 3 bar (43.5 PSI)

Thanks ainarssems: Very helpful.

7 tested 150-160 psi...the 8th was 180 psi....so it appears that's w/in range.

I've ordered a bore-scope w/usb for laptop to double check the cylinders & valves. Appears to be nice option...rather than just guessing...

General DCS050 Seeker 050 usb Video Inspection System
$44.95...no s&h since minimum order was $40...! Of course I am not sure about s&h for uk or europe...

http://www.testequipmentdepot.com/ge...2398?ref=gbase

Hope this might be helpful...Happy New 2011...Year !!!

[ainarssems]

That's cheap for bore-scope When I was looking for it, I could not find anything that I liked for less then £200. But I do see 2 problems with this one 12mm diameter will be tight fit spark plug thread outer diam is 14mm and inner will be 11.5mm if I am not wrong so You will have trouble getting it in unless You file/sand it down. Second is I cannot see any attachable mirrors included to change viewing angle. Ideally You would like to look down, to side and up. If there is no mirrors You will only be able to look down if the camera is at the end.

I could not find any I liked at the price I would like to pay so I ended up making one myself from the laptop internal webcam I had lying around and a white LED. Camera was facing to the side and I was attaching small mirror made from CD at the 45 degree angle so that I could see down or up as well. It was quite old webcam not very sensitive and not much light from one LED so picture was not very good but good enough