LED telltale for fuel pump prime

[pupp]

I'd like to add a simple LED on the dash somewhere that lights when the pump is priming (or even just running generally, matters not). I sometimes struggle to hear it and would find this helpful.

Am assuming it's just a case of piggy-backing a suitably rated LED off the pair that feed the pump... easy from the footwell spaghetti somewhere as the relays are in there? (I know this would be fooled if the pump itself was faulty but I'm not worried about that)

[Cider Andy]

It should be quite simple. Provide an ignition switched +12V feed to a standard 5mm LED via a 680 Ohm resistor. Connect the LED's cathode to the negative side of the fuel pump relay coil (terminal 85). This should light whenever the fuel pump is supposed to be running, irrespective of whether there's a relay or fuel pump fault.

Alternatively, connect a +12V supply from the relay output (terminal 87 or 87a) via a 680 Ohm resistor to the LED's anode and connect the LED's cathode straight to ground. This will only light the LED when there is a +12V output from the relay, so it wouldn't light if, say, the relay was faulty.

[spend]

Get a fuel pressure gauge or install a fuel pressure warning light.

Previous post will only tell you ECU & relay are switching pump ~ no guarantee electricity gets to pump or pump is working...

Seems a bit OTT, but each to his own

Dave

[GreenV8S]

What it *really* needs is a differential pressure switch to tell you whether the fuel line pressure is correct relative to manifold depression - but I've yet to find one. However I have spent quite a few weeks with wires back from the pump to a tell tale, and with the fuel pump relay run through a break-out with LEDs on all the circuits to show me what was happening, when I was trying to sort out problems with the V8S fuel pump supply. (I think I had just about every problem it is possible to get, all at the same time.) It's really the only way to nail down intermittent problem, but not something I'd recommend otherwise.