Fuel pump relay wiring

Discussion in 'Mech Tech' started by Gooders, Oct 26, 2019.

  1. I am wanting to fit a 5 terminal fuel pump relay to the electric pump. The type which switches the pump on for a few seconds when you turn on the ignition, then relies on a run signal to keep going.
    Question is will terminal number 1 on the relay (run signal ) work when connected to the coil-ve?

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  2. Yes.
    But the pump run when you switch it on is not a few seconds more like one second it is only intended to presurise a fuel injection line it won't fill a carb up.
     
  3. Yes.
    But the pump run when you switch it on is not a few seconds more like one second, it is only intended to pressurise a fuel injection line it won't fill a carb up and the relay with the integral fuse makes life easier.
     
    snotty likes this.
  4. If the relay time is too short, you can get variable ones. Or get your soldering iron out and change the timing capacitor inside the 1 second one.
     
  5. Not really worth the effort Snotts, electric pumps pump the fuel at a constant rate until they meet pressure and will fill the carb up much faster than a mechanical pump which is reliant on how fast the engine is cranking over.
     
  6. I think i am going to go with an ign fed timer relay to give it the first 15secs or so run time & swap the pump relay to alternator sensing on the trigger side. The only downside i see is if the alternator faults & stops charging you have no fuel pump. Not good on a smart motorway :eek:

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