350i IGNITION WONT SWITCH OFF?

[TonytheTVR]

Hi all,
My 350i has recently not been switching off when it turn it off at the key and I have even been able to remove the ignition key and the engine continues to run normally and I have stall it to stop it.
It doesn't happen when it's cold but has started happening when it's hot after a run out.

Has anyone else experienced this? And what may be the problem ?

Thanks in advance,
T

[SLB]

Hi Tony, wow that's a new one on me! I would guess it's a sticking contact in the ignition switch or maybe a sticking relay. I would try flushing the ignition switch with electrical contact cleaner and see if that helps.

[TonytheTVR]

Hi,
Thanks for the response, yes will start at the switch and so if that sorts it.
Cheers
T

[Adrian@]

Two versions of column over the build dates, (so pictures help) but both have minor screws to remove the ignition switch (the electrical side) from the key barrel, both have key barrels that relate to the key/steering lock only, then, the sprung return after starting is in the electrical part. It sounds like the switch (version dependant, Triumph or Rover SD1). You might need to buy into the connects to swap male female plug internals on a new switch.
A@

[TonytheTVR]

Cheers Adrian.
I'll investigate.

[TonytheTVR]

Any ideas though Adrian why its only occuring after it's hot?

[Adrian@]

No idea to be honest...I have TVR's with both version of the ignition switches (as the early Wedges rolled over from the M Series, Triumph version and then I have a very late 280DH using the SD1 version) it sounds like a mechanical/electrical fault in the switch. It is old school stuff and not for posting on an open forum, once you strip the column down. A@

[keynsham]

As I recall, all the ignition switch does is connect and break 12v to the coil. If it doesn't turn the engine off then the 12v to the coil is still live so the switch must be faulty. Most immobilisers work by just breaking this feed so when you try to start the car, there is no spark.

[TonytheTVR]

Cheers guys
Appreciate the views
T

[Polly Grigora]

Anyone's guess but......

If the switch contacts were welding together it is doubtful that they would only weld together when the engine was up to temperature and if they were welded together they wouldn't fix themselves later (they would remain welded together)

A mechanical fault within the switch would worsen over time and not only raise its ugly head when the engine was up to temperature

The above points to the fault being elsewhere but.....guessing and all that.....

There's more of a chance that the fault is being caused by a relay holding in when it shouldn't be

or

Alternator rectifier failing when hot

You could try disconnecting the alternator D+/61 warning light cable (Thin Brown/Yellow) from the alternator when the fault is showing

Happy hunting for the fault

[TonytheTVR]

Again,
Thanks. Something I will look at and try also.

[Skyedriver]

Does it continue running "for ever" or just a few seconds?
If the ignition is too far advanced or there is carbon build up in the head you'll get dieseling , run on with the ignition off. Used to get it in a mini with high compression.

[chj]

I had something similar to this and in my case it was nothing to do with ignition barrel or switches ... ended up being dodgy diode on alternator!

[jeremyc]

Is your cooling fan running when this happens?