Live alternator wire for delivery pump

Hi everyone.
I've fitted a diesel delivery pump down beside the rear fuel tank of my Y61 TD42ti and wired it up using a relay. It's all finished bar locating a live feed wire from the alternator. For safety reasons, I want the relay to lose its feed when the alternator stops spinning and hence kill power to the pump. Can anyone clearly tell me where I could find the required wire to tap into? The relay is attached to one of the wiper motor bolts so ideally I would like a wire that is in the fuse box area but if it has to come all the way from the the alternator then so be it. I've also been told that I will need to fit an in-line diode regardless of where I get the feed from. Is this true? I hope I've explained what I'm trying to do well enough. Any help would be greatly appreciated. Thanks, Deevo.

I think you simply need to find a wire that is live when the ignition is on and dead when its off. Pull out a multimeter and start prodding around in the fuse box, or to home in on it look for the accessories circuit or the cigarette lighter circuit perhaps?

Best way to my knowledge is a relay off the Alt warning light.
Use the NO contacts of that relay to power the coil of the pump power relay.

Logic will look like this;
IGN OFF - Pump relay open, no power to pump
IGN ON, - Alt Relay energised no power to coil of the Pump relay, pump relay open
IGN ON & ALT running - Alt relay de-energised, power to Pump relay coil, pump relay energised, pump runs.

How you handle the initial delivery lift for a cold start will stay the same as now

I’ve done mine using the oil pressure switch to earth when engine is not runnng. Pump is fed through 30->87a when relay loses the earth. Pump cuts out if engine stalls.
I also run mine for 5 seconds while glow plugs are heating. The TB45 ECU handles that as it did for the old EFI pump but it can be done with a cheap eBay digital timer.

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Originally Posted by jff45

I’ve done mine using the oil pressure switch to earth when engine is not runnng. Pump is fed through 30->87a when relay loses the earth. Pump cuts out if engine stalls.
I also run mine for 5 seconds while glow plugs are heating. The TB45 ECU handles that as it did for the old EFI pump but it can be done with a cheap eBay digital timer.

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Exactly what I did. Works a treat.