1987 audi 5000cs intermittent start Fuel pump/further clarification

[Eric Huppert]

Gentlemen,

Some clarification to my sons post and ongoing saga with his 5000!

Originally car had no start condition which included no spark and no fuel
pump. following items were checked and or replaced with parts from another
5000...

1  RPM and TDC sensors replaced with know good ones. also checked with
meter. Car originally had weak or non existent spark, but now has spark.
Although flywheel pin could be suspect, spark would "never" exist with bad
reference pin... Believe they also pinned out/metered wiring to ECU.

2  All grounds (ecu to manifold, and left side to chassis ) grounds examined
and cleaned.

3  Coil and driver exchanged with know good one, dist/hall sending unit also
replaced.

4  Fuel pump relay exchanged, they also checked voltage in relay slots per
SJM.

5  ECU swapped out. Original is my old IA chipped unit, but stock ECU was
swapped in to confirm it wasn't a bad ecu

6  Suspecting possible flaky ign switch, that was also replaced with know
good one.

7  They've run codes when car not starting, believe they came up with the
normal code for no start condition (speed sensor I believe)

My son and his friend have been through Scott M's site and done very test
that seemed appropriate. They've also utilized my Bentley set for the later
5000 - 200 series and run every check they could.

Prior to this car was running very well. He's had this one several months
now and was slowly getting it sorted out.

thanks for any input as I also am somewhat baffled!

Cheers, Eric