Starting problem

[Jonessa]

Our new minor has a strange starting problem, turn the key to second position and the pump runs as it should, when you turn key to third position and the engine cranks over but won't fire until you release the key, it takes 2 to 3 goes to get it to start, last owner says it has always done it. I have had a look at the ignition switch which is a Lucas switch but a lot larger than the normal one, it also has a recent coil which is gold and says it's a Lucas again, any ideas please.

[svenedin]

By 3 postions do you mean 1) Off 2 ) Ignition on 3) Ignition on +starter?

Do you mean that the car will not fire if the starter motor is turning the engine over but only fires when you let go of the key?

It would be helpful to post a photo of this non-standard switch.

Stephen

[Bill_qaz]

Check you still have close to battery voltage at the coil when engine is cranking.

[Jonessa]

Hi yes that is correct about the 3 positions and yes as you release the key to stop the starter turning it catches and fires, I will get a picture tomorrow if I get chance, I seen to remember something in the past about ballast and non ballast coils causing a problem like this.

[simmitc]

If non-standard switch, I wonder if in the start position, it removes power from the coil and diverts it to a non-existent second wire that in another car would be bypassing a ballast resistor? Is it as simple as low battery voltage that can't create a spark with the starter load?

Take a wire direct from the unearthed battery terminal to the coil feed. Now try the key. Does it start on position 3? You will need to remove that temporary wire to stop the engine

BTW, I'd probably refer to switch 0 = off, 1 = ignition, 2 = ignition + starter, but that's just being pedantic. Sorry, we understand what you mean

[Andmurph]

Our pickup does the same. I thought it weird initially and went through the wiring very carefully. I couldn’t find anything wrong. The car starts reliably in all weather conditions, cold, warm or damp so I put it down as a feature.
I’ve tried a couple of Bosch blue coils and have a distributor doctor distributor. I think the ignition switch is original.

IMG_9675.jpeg (2.84 MiB) Viewed 3209 times

[geoberni]

If non-standard switch, I wonder if in the start position, it removes power from the coil and diverts it to a non-existent second wire that in another car would be bypassing a ballast resistor? Is it as simple as low battery voltage that can't create a spark with the starter load?

It shouldn't be anything to do with the Ign Sw, the 'Ballast Coil' wiring should just be a 12v feed from the Ign Sw for normal running that routes via the Ballast Resistor, resulting in approx 9v at the Coil.
When cranking the Starter Motor, a separate 12 supply from the Solenoid bypasses the Ballast Resistor.


However, I do wonder about the Volts Drop on cranking it, especially if it has Electronic Ign...

Does it have conventional Points or Electronic Ign??

[Jonessa]

Hi yes it's still on points and still positive earth, unfortunately not had chance to try any of the suggestion today though.

[geoberni]

Hi yes it's still on points and still positive earth, unfortunately not had chance to try any of the suggestion today though.

Well it's certainly a strange problem, choosing to fire at the moment the Starter power is cut. The Plugs igniting the fuel mix at the very moment the engine is about to stop turning over...

It has to be a problem with the electrics, insufficient power getting to the Coil while cranking the starter.
Battery Terminal Voltage drops when the starter is pulling the current required to turn the engine over, but at the split second the starter stops pulling current, the voltage increases allowing significant increase in spark energy.
I'd be checking the quality of connections in the Ign wiring, including the quality of the Engine Earth strap.
For example, if the Earth strap connection isn't 100%, then when the Starter is cranking, due to the high current, a poor earth can result in a greater voltage drop across the earth point, thus resulting in less volts to drop across the Coil, equalling less spark.

[Jonessa]

Thanks for the pointers, I will have a look as soon as the new brake pipes are fitted just need the rain to hold off as she's outside at the moment.

[Jonessa]

Finally got the fault sorted new ignition switch fitted and she fired up straight away as she should, now onto next jobs. Thanks everyone for your help.

[svenedin]

Great to hear!

Stephen

[geoberni]

Great news. Thanks for reporting back, it's good to get completion to the story.