Tachometric relay question

I am trying to diagnose why my 91 Euro TR suddenly started running on one bank. Investigations are still at an early stage, but at least I know the fuel pump relays and fuses are good. Car gets spark on both banks, so the coils and distributors are good - I am looking for a fuel issue. Fuel pumps are OEM and a year old.

I did wash the car beforehand, but cannot see anything amiss in the engine room. I am fortunate to have the Ferrari diagnostic breakout box and ran through the KE jet diagnostic list to check voltages and resistance, everything checked out.

One pin is burned on the horizontal Y connector at the fusebox. I still have to check what that pin goes to, either a fuel pump or a radiator fan (I suspect the latter as the left side fan stopped working with a burned fuse a few days back). I need an upgraded fuse box.

If the tachometric relay fails, both fuel pumps stop working? It would not make sense otherwise as a safety feature.

I recall a bad O2 sensor making the car run rough about a decade ago. I don't think it can cause the car to run on less than 12.

Does anyone have a diagram showing which horizontal fusebox connector is which? I foolishly disconnected all of them and forgot to label them.

This evening I will replace the burned pin and check spark for each cylinder, along with the manifold temperature of each bank. I need too see which bank is not working.

Anything obvious I am not checking? I will also resort to seeing if the pumps are delivering fuel.

 

Many thanks, exactly what I needed. I love the car, one reason is that I am usually ‘just’ smart enough to figure out what is not working on it.