According to the diagram of the P8 Pro, the ecu main supply is on Pin 26,
The motronic ecu is supplied direct from battery via a 3A fuse. Use this as a main supply for your ecu, if there is not a supply cable there, add one.
It looks as though control for fuel pump is received from P8 Pro pin 28, is this a battery supply or earth signal ?
Depending on which it is, decides whether you need to wire in a battery or earth to other side of relay solenoid.
Basically if you receive an earth signal from ECU, you need to wire in a battery to other side, so when the earth signal is receive, the relay activates.
If you receive a battery signal from ecu, then you need to wire in an earth to other side.
You then use the other pins to supply the battery to the fuel pump.
Relay pins are :-
30 - Relay switch side a
85 - solenoid side a
86 - solenoid side b
87 - Relay switch side b
87a - Relay switch side b
Eth + Batt across 85+86 should cause a short across switch between 30 and 87/87a
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