This morning on the way to the hangar I bought some more ceramic disk  capacitors 0.01mF as suggested. Tried them on the fan. No change. The  fan is Spal brushles I think? It has separate return line to the  engine case.
While waiting for Jim to come with the oscilloscope, I connected  (temporary) the large 20A Radio Shack noise filter to filter the  incomming power to the avionics bus. BIG improvement! I would say 80%  reduction in fan, fuel pumps etc. noise.
Jim arrived with the o.scope and we connected it to the fan. Wow! You  can see the noise. Started trying different disc capacitors I had and  they did not make any difference. Jim asked me to buy few different  ones at RShack and left to take care of business, but left me the  o.scope. After trying few capacitors, 475mF did the trick.
Now the high pressure FI pumps. They were making one hell of a noise  filling the whole screen on the scope.
The avionics filter was taking care of most of it, bit I can still  hear them. Went twice more to RShack for bigger and bigger  capacitors. Finally the 2000mF made difference on the screen, but not  enough. On the way home I stopped again in RShack and got the biggest  one they had 5000mF and hope in the morning to see a flat line on the  screen :).
Next is the alternator, but had no time to run the engine today.
Thanks to everybody for your suggestions.

QUESTION FOR TRACY: At all times with everything else turned off  except master, I hear quiet noise in the headset that's like a clock  ticking. If I disconnect the antenna from the radio it stops. I was  wandering if there is something in the EC that maybe doing this?
Buly





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