What are the chances???

[Tea]

Well, we've managed to fail our M.O.T before even leaving the house this morning

I tried to start our standard 1968 Morris Minor and it didn't quite go to plan.

After turning the ignition switch he started trying to turn over without firing up and without stopping trying to turn over even after removing the key. I had to disconnect the battery to stop it. Now when touching the terminal he sparks like nothing else.

This is the 3rd time it's happened within a year. Both other times it's been the ignition switch.

What are the chances of this happening 3 times in such a short period of time? Could there be an underlying problem or just bad luck?

We had first thought it was the solenoid becoming stuck.

It often seems to be around the same time as a battery dying (not sure if this is again bad luck with batteries or the dynamo...)

Thanks for any help.

[blues2rock]

The best way to check is to leave the battery disconnected and simply place a multimeter (set to ohms or continuity) across the two big terminals of the solenoid. There should be no connection between the two. If there is the solenoid is faulty.


Be VERY careful about sparks because they could cause the battery to explode especially if it has recently been on charge.

If the solenoid appears ok you can confirm a switch problem by placing a test lamp between the thin lucar wire that you previously removed and earth. Then operate the switch through off/on/start several times and check that the test lamp only illuminates in the start position.

If it is the switch then either you have been very unlucky or there is some problem with the way it has been fitted - but I can't see that being the case. Either way get the new one from a different supplier and avoid the very cheap rubbish.

[bmcecosse]

To test the solenoid - pull the white/red wire off and then connect the battery - obviously the engine should NOT turn over. Is it a relatively new Ign switch? And does it feel 'sticky' when you turn it - or does it spring back ok?

[blues2rock]

It's very rare but I have to challenge BMC on his method - yes it's quick and easy but VERY dangerous. If the solenoid is closed the current draw is very high which = very big sparks. Tea got away with it when disconnecting the battery (Hobson's choice really) but if you value your good looks and more particularly your eyesight don't risk it.

[bmcecosse]

Can't see any great risk in it myself. It's what I would do. It's not a huge current - there's no suggestion that the starter is seized/not turning. If a meter is available it could of course be used to check the solenoid, or the Ign switch - or even a bulb with wire attached....... Only a 'touch' with the battery connection is required - and it's v unlikely to be a stuck in solenoid anyway!

[Tea]

White/red off and it's still sparking away. I take it that this means it's the solenoid?

[Tea]

Also the ignition switch springs back nicely and was taken from either an Austin Van or Morris Traveller.

We've not yet used a new switch (first was the original and second was the above), we have however got a 6 month old Lucas solenoid.......

[bmcecosse]

I'm afraid it does indeed mean a very rare 'stuck solenoid'....oh dear.

[Tea]

That's 2 in 6 months!!!! Neither were supposed to be cheap rubbish, but even the 'good' seem to be not so great.

Oh well!

Many thanks

[bmcecosse]

Try to find a good old solenoid - the one with the rubber button on the end. Perhaps like this one - although not the nicest looking one - if it works, the price is right! http://www.ebay.co.uk/itm/MORRIS-MINOR- ... 5afb2232cb
This one looks a bit better - although rather expensive postage... http://www.ebay.co.uk/itm/Lucas-starter ... 338a6f6b7c

[Tea]

Awesome! Thanks for the links, it's much appreciated

[MarkyB]

That's 2 in 6 months!!!

It's possible that solenoids are reaching "end of life" nothing lasts for ever, possibly some insulation starts to break down after 45 years

[bmcecosse]

The ones that have failed....are they the 'rubber button' type - or the newer 'can' type?

[Tea]

Newer can type. Both purchased brand new. The older are definitely of better build quality, so will be getting one and keeping the new one as a spare for emergencies.

[MarkyB]

The new ones have a short life expectancy, often Very low!

[bmcecosse]

I would definitely avoid the new 'can' type - and probably the new 'button' ones too - probably made in the same tin hut as the new (useless) coils.......

[alexmcguffie]

Sounds like the contacts in the solenoid are made of a lower grade material that is welding together when the starter current initially passes through them. As for batteries exploding when a current is drawn, very very unlikely!

[blues2rock]

The possibility of battery explosion is certainly NOT "very very unlikely".

People posting advice should remember that many of the 'readers' are not trained mechanics or experienced tinkerers and may take what is posted as gospel. They could end up being seriously injured as a result.

I would agree that if a lead/acid battery has been unused - ie. 'off charge' for at least 72 hours in a well ventilated space then it is unlikely that hydrogen gas is being produced and so the risk of explosion is very small. However if it has been 'on charge' and that includes being used in the car, then there is a real danger that a spark - particularly a big fat one such as we are discussing in this thread - will trigger the rapid burning that we colloquially call an explosion.

Any first year mechanical student would be aware of this.

[alexmcguffie]

Ok blues2rock there is a chance of an explosion but again very small. In 25 years of working in motorsport and on classic cars I have never seen a standard car battery show any sign of exploding.

I also used to work with mechanical students and I wouldn't trust them with electricity!

[bmcecosse]

The point was about a battery 'exploding' when current is drawn - this is NOT going to happen. Otherwise there would many exploded batteries every morning as folks start their cars! Yes - spark has a faint chance of causing an explosion - on a freshly charged battery......but again very unlikely unless the battery is STILL on a high charge rate - and gassing off hydrogen. Remember -hydrogen is the lightest element - and it doesn't hang around for long when released into the atmosphere...... Also the solenoid is generally mounted below the battery - and any hydrogen is going to be headed UP, not down..... Much more chance of an explosion if smoking a fag -and hanging over the battery...... Definitely not advised........