Engine runs on with key out

[Iain]

Had my engine running for the first time on carbs with no alternator and it was fine

Just had it running now and gone to turn it off and it carried on, had to use the killswitch to kill it off

Since the last run it's had the alternator fitted and the auxiliary items properly fused. It's on R1 carbs and H&H dizzy. The coil and fuel pump are wired into a relay that takes +ve from the killswitch and is triggered by an existing ignition live off the Nova loom.

The dizzy gets 12v with the key on, 0v with the key off, start it up and it's at 14v, key out after running and it stays at 14v

What's happening? Alternator backfeeding something? Wired up the relay wrong?

[Iain]

Couple of dash lights on really low too

[therealnovaboy]

Yeah I had this. The alternator back feeds the ignition. I ended up putting a diode in to stop it. It's been fine ever since.

[mowgli]

time to rewire it as a carb engine.

[Iain]

I've done quite a substantial rewire on it... I may have used a different existing ignition live to trigger the relay so maybe I'll try swapping that.... I do recall having this issue when I first built it and finding a different ignition live source sorted it.

Not sure about a diode it feels like avoiding the problem. Would that be on the white/blue?

[therealnovaboy]

It's not really avoiding a problem it's engineering a solution. It was a while a go I did it and can't remember what I'd need to look at a diagram again. if you need to know I'll find have a look.

[therealnovaboy]

I think it was the wire to the battery light wire I put the diode.

[Iain]

Yeah the blue/white wire... I'm sure its the black wire I've used the more I think about it... There must be some ignition lives that aren't cut off by the ignition switch

[torquey]

I had this due to my clocks the pcb was broke causing one of the track to touch and would keep the engine running with no key.

[Walshysr]

I've recently had a similar problem in my van it was all down to a cheap light I had plugged into the cigarette lighter and was back feeding so my van would not shut off haha had my puzzles for about 10 minutes out side the shop