Ignition switch fault?

[welshrat]

Bit of an odd one this, without warning my minor decided not to start, under the bonnet with ignition on I pressed the solinoid button, started first kick. I was very pleased as able to get home, the problem remains, will not start on the key but will on the solinoid. I am thinking its an ignition switch fault but would welcome any thoughts before I start tinkering.

[Biggles1957]

I had a similar problem a few weeks ago - after much twiddling and scratching about it was the solenoid coil itself - ign switch was fine but the soleniod had just got too 'tired' to pull the contacts in properly each time. I suspect that over the years the main contacts in the soleniod were most likely worn too cos they do have to handle a considerable current each time you start the engine. Straightforward to swap the solenoid although my new one no longer has the little rubber button you can push - I needed one quickly and its all my local car shop had on the shelf so I will get a proper one and swap it sometime!

[welshrat]

Mine is doing all the right things on the key, as in turning engine over as per norm, just appears to be no life, gonna check if I have a spark on the plugs when turning over with key, my money is on there being nothing.

[MarkyB]

If the starter is using too much power there can be none left for sparks.
I'd take it off, and give it a good clean while you check the state for the brushes.

[welshrat]

If the starter is using too much power there can be none left for sparks.
I'd take it off, and give it a good clean while you check the state for the brushes.

If it was starter motor related it would present with the same problem when using the solenoid to start the car I would have thought, there are no issues at all when starting it this way.

[bmcecosse]

How strange! So - it turns over ok when using the key - just won't fire. But fire's up right away when you press the solenoid - is that correct? If so -I guess your diagnosis is correct - but it's very unusual failure!!

[welshrat]

How strange! So - it turns over ok when using the key - just won't fire. But fire's up right away when you press the solenoid - is that correct? If so -I guess your diagnosis is correct - but it's very unusual failure!!

Spot on, not had chance to get to it today as hoped but off tomorrow so first thing for me is to check if there is a spark on plug when using key (I think there wont be) then see if there is a spark on plug when using solenoid (must be as starts first kick). Going back to the original question and the above being the case, could it be anything else or would the prime suspect be the ignition switch?

[mike.perry]

If all else fails, try the starting handle

[beero]

I have heard of an MGB ignition switch going faulty like this. When the key was in the starter position and cranking the engine there was no power going to the coil, release the key and power returned to the coil.
Do you have a meter or test lamp that you could attach to the coil to see if this is happening in your case?

[welshrat]

After a bit of tinkering it appeared that there was no spark on plug when using key and healthy spark when using the solenoid, as I thought but cannot really explain why. What I do remember is having a simular problem with a mini many years ago and after spendng a fortune on changing everything else I tried a new ignition switch which done the trick. Just good luck that I had an old steering lock and ignition kicking around so swopped the bottom part over, now all seems to be well.

[MarkyB]

I already explained why, the starter motor and associated gubbins use up all available juice.
Operating the solenoid uses a significant amount, if you take it out of the equation by DIY there is enough for sparks, it isn't that rare., honest!

[welshrat]

I already explained why, the starter motor and associated gubbins use up all available juice.
Operating the solenoid uses a significant amount, if you take it out of the equation by DIY there is enough for sparks, it isn't that rare., honest!

Hi markyB, I understand what you are saying and i have come across this before with a faulty starter motor, however on this occassion I do think it was a faulty ignition switch as the probem has gone since swapping it for a different switch. Beero is describing the fault that I had above.

[MarkyB]

Fair enough, I've seen a lot more starters need attention than ignition switches and one fix is a lot cheaper and simpler than the other, being a dreadful old chaepskate the ignition switch would be low on my list fo priorities but it would still be there.

[mike.perry]

I have had the same fault in the past, turn on ignition start, engine turns over, release key, engine fires. It always started

[bmcecosse]

I agree - it seems too 'certain' to be caused by a low volts problem. The new switch has solved the problem.......

[welshrat]

Correct, I quickly realised that if I released the key from position 3 the engine would fire up, however prior to Saturday to start the car was just a case of turning the engine over on the key until it fired, so sat in Sainsbuy's thinking AA call out. Not so good on first start up in cold weather tho so decided to replace the prime suspect which has put starting the car back to supermarket visit.