Fuel pump relay and other starting issues

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Clarkeatron

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Hi all, so quick electrical question. I have fitted an electric fuel pump to my 68 baywindow and it is great, but I bought a relay kit which uses a 5pin relay. The wiring is linked to the coil. The wiring set up was using an 87a connection which is a NC connection so the pump automatically turns on when the ignition is primed. Not good, because in a stall condition it will still be running. So I tried swapping the 87a with 87 pin on the relay. Now the priming switch turns on but the pump does not, even once the ignition switch is turned over. I have a similar issue with the alternator where the light doesn’t go out, but if I rev hard enough it supply’s enough voltage to complete the alternator circuit and the switch goes out. I think they are related (i.e the relay isn’t getting enough voltage to switch the relay) or I’m missing something obvious. Any ideas would be greatly appreciated?
 
You will need two relays to achieve what you are trying to do. The NO contact of one relay will fire the coil of the other and the supply taken from the coil and the output from the alternator. So if the ignition is off and or the alternator isn't making a voltage the fuel pump will not pump fuel. I think I posted the drawing on my gallery thread........somewhere
 
UPDATE: So good news all I’ve fixed it! Turns out it was a combined issue. So the alternator light wasn’t going out because I changed the ignition light to leds but the voltage was so low there wasn’t enough power to register it until you rev the engine that is.I changed the lights back to normal bulbs and the alternator light goes out immediately. I changed the pump link to the alternator rather than the oil pressure switch and it’s all working and the prime switch works as it should. Only problem now is the oil pressure switch not coming on, but that could be a failure in the switch so I’ve ordered a new one. Thanks for all the comments. Much appreciated
 
Hope you’ve not put LED’s on the indicator tellbacks too … that’ll have you chasing your tail if you have 🙈.

Have you proved that the oil light lamp is working as hose lamp holders are a bit of a faff
 
Hope you’ve not put LED’s on the indicator tellbacks too … that’ll have you chasing your tail if you have 🙈.

Have you proved that the oil light lamp is working as hose lamp holders are a bit of a faff
Thanks yeah I’ve taken them all off for now. I did check the lamp and it is working, i tried plugging into the oil light but the light comes on and stays on when the ignition is not on, I think that suggesting an open circuit or a ground maybe?
 
Thanks yeah I’ve taken them all off for now. I did check the lamp and it is working, i tried plugging into the oil light but the light comes on and stays on when the ignition is not on, I think that suggesting an open circuit or a ground maybe?

The Oil switch is a grounding circuit. Unplug the wire from switch and turn on ignition and the lamp should be off. Ground the cable against the casing and the light should come on. If it doesn’t you have a problem with the wiring. If the wiring is ok then it must be the switch 👍
 
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