Hi Art,

I believe you might be on to something because he said he could hear the relay.
I accused him of having very good hearing or very long arms to hear it click! That thing is no large AC motor, starting contactor.

I have seen several relays with diodes in them, when another relay, that looks exactly the same, will not have them. I have always assumed that difference was for AC operation verus a smooth Non-rippling supply.

I mentioned I saw one in the circuit but I have no idea for it except back feed coming from the controller boxes that turn it on.

Did he say that the car was running or that the relay was quieter?
Did he say he suddenly got the 12 volts on the orange wire or that the fuel pumps ran?
Has the car started or even run? It's easy to miss details, written or not!

I was leaning more in the direction that the ECU ground might be corroded as well.
You are right about finding good ground points for the meter leads too.

I was about to ask him to try checking, with his meter for any voltage rise ( an opposition causing some voltage difference) on any of the grounded wires back to the negative post on the battery. While he has something turned on in the car or the troubled circuit is nice.

A bad "body" ground cable could be in play here because they look sooo innocent!
We won't know until he get the car farther along into a running condition to see if he has any charging or lighting problems.

Phil