Engine Will Not Turn Off

[gmlaverda]

After a ride I turned off the ignition key and the car kept running. I had to use the battery disconnect in the trunk to turn it off. I have a professionally restored 1955 BN1 with several hundred miles on the restoration.

Initially I suspected the ignition switch was the culprit, but disconnecting all of the switch wiring and isolating them does not change anything; the car will still start and run.

At the fuse block all of the wiring reads 12 volts with the battery disconnect on and the ignition switch off. I have not altered any wiring recently.

Any ideas on what I should check?

Thanks, Gary

 

[Healey Nut]

When you say the car kept running, was it running normally or was it a little uneven/ pluttering. i.e., “running on” as they say? Healeys run hot and can, if the conditions are right, “overrun" once you turn off the key. They kind of cough and splutter and eventually quit. It’s just that everything is so hot and there’s enough fuel vapour in the carbs and engine parts heat up, etc. and they just keep going for a few seconds after you turn them off. It usually only happens after long runs in hot weather, in my experience.

Power to the fuses with battery switch on and the ignition off is normal.

 

[NutmegCT]

" I had to use the battery disconnect in the trunk to turn it off."

If disconnecting the battery caused the engine to stop, seems that would eliminate a run-on problem.

 

[LarryK]

Check for a hot wire to the coil. Seeems a bypass was miswired and not affected by ignition.

 

[gmlaverda]

The car was not "running on". In fact the next day I was able to start it cold by simply pressing the starter button with the battery disconnect turned back on. This was with the wiring to the ignition switch completely disconnected and isolated.
Today I am further confused. There are 3 wires at the switch, one brown wire (unfused and always hot) and 2 white wires that are switched on with the key. One of the white wires was reading 12 volts while disconnected and it should not. One white runs to the starter button I believe and the other to the coil. So I decide to pull the fuses and check for voltage at the white conductors on the fuse block thinking there is a backfeed or short circuit somewhere. I read no voltage. I put the fuses back and everything is now operating normally. I have no idea what is going on but the car is fine now and the ignition switch works. I sure would like to know what was wrong in case I experience this again.
Thanks, Gary

 

[red57]

OK, This is a real shot in the dark but....The white wire that goes to the coil continues on the lower fuse in the fuse block and supplies the power to all the accessories. In the fuse block, there is a bakelite post/pin that sticks out between the fuses (this post also holds the metal clip that holds spare fuses in), if this post is broken off/missing it's possible to put a fuse in in such a way that it bridges the 'always hot' brown upper circuit and the sometimes hot accessories circuit. I said it was stretch but I offer it as something to check.

 

[gmlaverda]

My fuse block looks a little different without the post and the clip is riveted on. I'm sure what happened is something bizarre as you have suggested. Now that you have mentioned this how exactly are the spare fuses held?

 

[red57]

Interesting I didn't know there were different fuse blocks - I have two, a BN4 and a BT7 with the pins, I see yours without the pin but I don't know if it's possible to put a fuse between the contacts - it looks like there are small triangular points sticking out between the fuses that could prevent one being installed wrong...I said it was a long shot. Could there have been something else bridging the two fuses?

I attached another picture to show the spare fuse holders, that's what the other metal thing is for, keeps some spring tension on the spare fuses so they don't fall out.

 

[gmlaverda]

Mine appears to be fine. Thanks for the info about the spare fuse holder. I had no idea. Still scratching my head about the electrical issue though.

 

[BN6_L1232]

This same condition occurred in my Healey when a short in stop lamp circuit melted the insulation of the stop lamp and the horn circuit causing power to be feed from the horn wire to the switched ignition circuit. This occurred within the loom near the firewall.
I believe I had the incorrect fuse in the switched ignition circuit which allowed more current to flow in the green wire circuit thus melting the wires causing the insulation of both the green wire and horn circuit to join.

Had to disconnect the battery to get the car to shut off.

A Buss fuse instead of a Lucas fuse was, I believe, the cause. More current was allowed to pass through the wires heating them up beyond the melting point of the insulation.

 

[gmlaverda]

Thanks for your input. I do have my taillights separately fused but I had envisioned a problem similar to your description. I was really just getting started to learn the wiring and do some troubleshooting and then the problem just went away. It may surface again. Intermittent electrical issues are fun!