Thunderr

Hello guys.

I'm swapping the engine out from an Audi A6/C4 2.8 V6 (AAH) in an Audi 90 NG.

I got the engine wiring harness in, tho NO engine in place.

I wire up the ECU, green to the fuel pump relay (I used the 2.3 Audi 90 relay I had), black to 15, and black/green with that grounding "o ring" end to ground. small red goes to 30 (B+) and that's it. I haven't hooked up anything, because its not needed as by the schematics.

I turn the key to ignition with the ECU in place but no engine, fuel pump relay engages and primes for 2-3 seconds and shuts off. I turn the key to off position, then to ignition again, NOTHING. Absolutely nothing happens. I tried removing the battery terminals and putting them back in to reset the ECU; no. I have power everywhere I should. Afaik I only need the yellow thermo-fuse holder to be on when the key is on ignition. The relay does NOT engage no matter what I do. It almost sounds like it wants to, but sounds like it has no power? It shakes JUST A TINY bit when key is on, but it does not move the contact points in the relay.

My question is, could I have fried the ECU in any way? I read that fuel pump wont prime or turn on at ALL until engine is being cranked at min of 28RPM? Is that true?

I really hope the ECU is not gone. I need all the help and info/advice I can get here.

Rusty Spokes

I don't think you fried anything..without an engine in place..there are no sensors inputs like temp, camshaft position, air mass meter, etc ..so the ECU closes down..my opinion.

Thunderr

Thanks for your answer! ECU's are very rare here to find and very costly. I'm looking at about 250$ for repair and about 900-2000$ for the new ECU.

Cheers.