Leaving the ignition on

54kroc · 01-06-2011 03:05PM #1

This is probably a silly question but when I was a young fella learning to drive I was always told not to leave the ignition on in the car as it would burn out.
Does it burn out or is that a myth, will anything happen at all?

Kid Nothing · 01-06-2011 03:16PM

When you have the ignition on, you're pulling power from the battery to use your consumers (lights, radio, air conditioning, etc), you'll drain the battery in no time.

Why would you want to leave the ignition on?!

ArphaRima · 01-06-2011 03:23PM

Burn out? I think they mean the starter motor for an engine that is turning over. Even then the battery would probably die before the starter motor.

The only thing you are degrading by keeping the car powered without the engine running is the battery.

54kroc · 01-06-2011 03:26PM

Kid Nothing wrote: »

Why would you want to leave the ignition on?!

I wouldn't, I was telling someone not to leave it on and they were asking me about it, all I could tell them was the old fella told me it would burn out.
I just wanted to know what if anything would happen.

54kroc · 01-06-2011 03:33PM

After a bit of googling I read you could burn out the points in the distributor.
I guess that's not going to affect most modern cars.

Anan1 · 01-06-2011 03:34PM

I remember hearing the same thing, years ago. I was given a reason at the time, but it's so long ago - maybe something to do with the coil?

blacktalons · 01-06-2011 03:39PM

cork45 wrote: »

I wouldn't, I was telling someone not to leave it on and they were asking me about it, all I could tell them was the old fella told me it would burn out.
I just wanted to know what if anything would happen.

your "old fella" is partially right,years ago when all cars had the old "contact points" distributer ignition system ,if you left it turned on they would overheat/burn out. but all thats a few years ago now;) .how old is your ould fella :rolleyes:

kona · 01-06-2011 03:51PM

Its actually the ignition oil that burns out, What happens is it overheats as the engine isnt running and the points don break the magnetic field in the induction coil.

Anubody with an older car can check by turning the ignition to on and feel the coil after a few minutes, it gets noticabley hotter.

the culture of deference · 01-06-2011 04:19PM

It is a valid question nowadays because of all the cars with stop start technology. I know the alternators and starters have been strengthened in cars with SST.

Years ago though my da would have said the coils would burn out, but cars were sh1t then compared to now. It brought back memories of my 1st car in 1987 and the knack you needed to start it. 2 quick turns, choke, 2 pedals pumps, and as she fired up fiddling with the choke.

Nowadays I push a button

Stinicker · 01-06-2011 06:58PM

I was always told this too, I think it comes from Diesel cars that by leaving the ignition on you'd burn out the heater plugs, which was probably a possibility in older cars before they turned them into computers with wheels.

slimjimmc · 01-06-2011 07:37PM

Stinicker wrote: »

I was always told this too, I think it comes from Diesel cars that by leaving the ignition on you'd burn out the heater plugs, which was probably a possibility in older cars before they turned them into computers with wheels.

Leaving the ignition on in a diesel has no damaging effect on heater plugs, unless you're constantly switching it off and on every 10 mins or so.

In some older car the plugs started heating as soon as you opened the driver's door so that by the time you had the key in the ignition they were already hot.
Also heater plugs had a timer which turned them off after a preset time, I think 7 mins. Even in old indirect injection engines the plugs stayed on long after the engine was fired up and running. The idea was that hot glow plugs would help ignition until the injectors reached full temp and optimal atomization of the fuel was achieved. A thermostat was used to shorten this post ignition time somewhat during warm weather.

dr.fuzzenstein · 01-06-2011 07:45PM

kona wrote: »

Its actually the ignition oil that burns out, What happens is it overheats as the engine isnt running and the points don break the magnetic field in the induction coil.

Anubody with an older car can check by turning the ignition to on and feel the coil after a few minutes, it gets noticabley hotter.

Wow, never knew that.
I knew you couldn't leave your foot on the gas pedal as you'd flood the carbs and the car wouldn't start.:D

kona · 01-06-2011 08:40PM

dr.fuzzenstein wrote: »

Wow, never knew that.
I knew you couldn't leave your foot on the gas pedal as you'd flood the carbs and the car wouldn't start.:D

On some carbs it was a kind of technique to push the throttle to reset all the cams and choke, then pull the choke out and start it

Old Cars are great, not a sensor or ECU in sight. Most things solved with a basic toolkit

and every one had a little "procedure" to starting

. All set up with stuff you learn in labs in college such as pressure drops and bernoullis equation

, may not be accurate as needed but its sure as hell more fun

ianobrien · 01-06-2011 10:36PM

kona wrote: »

may not be accurate as needed but its sure as hell more fun

And sound infinitly better. Twin 48 Webers breathing at 8 to 9k - Sweet Music.......

end a eknny · 01-06-2011 10:49PM

it was the old style coil aluminimum cylinder with a lead to the distributor cap. that would burn out

YouTookMyName · 01-06-2011 10:50PM

Could you flood the engine too?

langdang · 01-06-2011 11:21PM

YouTookMyName wrote: »

Could you flood the engine too?

As a special request to you? or wha;)?
Man, must be getting old if people don't recognise or understand the phrase "flooding the engine"!

No disrespect YouTookMyName, just grumpy old ramblings probably...

YouTookMyName · 02-06-2011 12:43AM

langdang wrote: »

As a special request to you? or wha;)?
Man, must be getting old if people don't recognise or understand the phrase "flooding the engine"!

No disrespect YouTookMyName, just grumpy old ramblings probably...

I only said it because i done it once to a '95 primera i think it was when i was a kid. Can't do it anymore.

David09 · 02-06-2011 01:28AM

I was told of something similar by a guy who repaired machinery. He was talking about a jcb digger. If the key was left on without the engine running, a warning buzzer would sound. If ignored and left for long periods, the device could heat up, melt and have the potential to set the cab alight.

Maybe he was just being over-cautious...

langdang · 02-06-2011 07:08AM

YouTookMyName wrote: »

I only said it because i done it once to a '95 primera i think it was when i was a kid. Can't do it anymore.

I misinterpreted your first post so!

drBill · 02-06-2011 08:13AM

kona wrote: »

On some carbs it was a kind of technique to push the throttle to reset all the cams and choke, then pull the choke out and start it

+1

My first car was 8 years old and had a sticky automatic choke. Eventually figured out that flooring the accelerator before cranking the engine would reset it and all would be well. To this day I'm still firmly in the habit of doing the same thing even in my current car which is only a few years old. In fact I do it for tractors, vans, everything.

kona · 02-06-2011 11:43AM

drBill wrote: »

+1

My first car was 8 years old and had a sticky automatic choke. Eventually figured out that flooring the accelerator before cranking the engine would reset it and all would be well. To this day I'm still firmly in the habit of doing the same thing even in my current car which is only a few years old. In fact I do it for tractors, vans, everything.

May still be relevant if your using a TPS as the Load sensor, and pushing the throttle will reset the linkages and the TPS. Wont do much about the choke thats all contained in the ECU, funnily enough the enrichment doesnt last that long, maybe 10 seconds.

Joe 90 · 02-06-2011 11:57AM

ianobrien wrote: »

And sound infinitly better. Twin 48 Webers breathing at 8 to 9k - Sweet Music.......

Indeed. I don't miss struggling with the points under to front Weber of a Lotus/Ford twin cam but I do miss the induction noise.

Leaving the ignition on

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