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Thread: Live alternator wire for delivery pump

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    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.

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    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?

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    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
    Dolphins are so smart that within a few weeks of captivity, they can train people to stand on the very edge of the pool and throw them fish.

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    Patrol Freak jff45's Avatar
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    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.
    John

    2001 GUII TI 4500 - Now converted to TD42T auto with Nomad valve body

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    Quote Originally Posted by jff45 View Post
    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.
    Exactly what I did. Works a treat.

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    jff45 (20th April 2018)

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