Ignition troubles

[Errol]

Hi

I have a Morris Minor with intermittant starting troubles and I'd dearly love any help you could give me.

Every few weeks the engine won't turn over at all. Eventually, I've been able to work out that when this happens, the actual problem is that the sparkplugs aren't firing (by taking one out and resting it against block then turning over starter).

But I'm not sure if the problem is the coil, the distributor or even just the ignition key (as you'd know, with ignition turned off, the engine will still turn over but not fire).

So I tested voltage on the two low-voltage terminals of the ignitiion coil. Looking down, the LHS terminal goes into the wiring loom. RHS terminal goes to the distributor. (I didn't check voltage on the big thick hi-volt terminal that also goes into the distributor.)

When the car is operating okay, ignition switched on but engine not yet running:
LHS 12v
RHS 0.6v

When the car is operating okay, engine running:
LHS 12v
RHS 4-6v

When intermittant problem occurs and engine will not fire:
LHS 12v
RHS 12v

Is that enough to tell me what the problem is? Is it the coil that's at fault?

Thanks HEAPS in advance!!

Errol Hunt
Melbourne, Australia
1959 Morry thou
1969 Austin 1800



errol.hunt@lonelyplanet.com.au

[Alec]

Hello Errol,

LHs is ignition supply which is fine at 12V. RHS is the distributor connection and with the points closed should be near zero volts. With the engine not running you may get either a low voltage or 12v depending on whether the points are closed or open, which is just pot luck, depending on where the engine stops.
I would check your points as a first step.

Alec

[Errol]

Thanks Alec, yes my (more technically competent than me) mate pointed out that the RHS voltage would vary acording to the points. Der!

What exactly would I look for in checking the points? Can they fail intermittantly like that? Is there an idiots' guide to checking points out there on the Internet somewhere?

[Alec]

Hello Errol,

if they look rough, sooty etc at the points then change them and set the gap accurately, then you will need to reset the timing. If you don't have one, invest in a workshop manual to guide you.
The voltage check is a good check when they are closed, as I said you should have a reading of around 0.2V to 0.3V, anything higher indicates poor contact and will seriously affect the HT voltage.

Alec

[57traveller]

This is unrelated to Errol's post but thought this could be a good place to warn that there are still some faulty rotor arms around.
I stopped to assist a fellow Moggie owner this morning, in layby with bonnet up and ignition bits everywhere!
Spark at points but nothing at plugs. He'd changed everything except rotor arm which was a "genuine" Lucas item which was only recently purchased and fitted. Remembering previous postings I suggested a rotor arm change, fortunately I had a used known good arm with me which was fitted and did the trick. So they're still around even Lucas parts! Very odd because it looked perfect, there were no prior warnings until engine "spluttered" a couple of times then died and wouldn't start again, not even a hint.

[Pyoor_Kate]

And those cruddy misshapen distributor caps are also doing the rounds, and appear to be at several mog specialists.

Check them carefully when you put them on, some of them look okay, and hold the HT leads okay only to get swiped by the rotor arm on it's way round - leaving a huge big groove in the contacts on the distributor cap and to a very quick degeneration in engine performance :-/

[minor_hickup]

Don't forget to check the HT leads with a multi-meter, you'll feel an idiot if its just a set of leeds you need, although your car would probably be misfiring while running if it was the lead(s).

[bigginger]

Mine started misfiring and died today, in the space of about quarter of a mile. Turned out the king lead (coil to Dizzy) had snapped INSIDE the plug into the coil. Could yours be going the same way? If only all electrical problems were as easy as that one...

[Willie]

ERROL, when your car is reading 12v on both coil terminals the
points are NOT closing.(you only read 12v when the points are OPEN).
This could be just bad contact faces on the points or trouble with the
flexible leads etc which are connected to the points spring anchor.

[Errol]

How do you check the HT leads with a multimeter? I thought voltage would be too high and fluctuating too fast? Would love to know how to do it for future reference though! (Short of grabbing hold of a lead in one hand and turning it over!)

I'm pretty sure i found the culprit: a sticky rotor button. (That little sprung button that sits inside the distributor cap and carries the HT to the rotor.) Each time the car fails to start I've whipped the cap off, given the button a few flicks in and out to loosen it, and then the car has started. Yay! Won't know 100% until I've replaced the thing of course but I'm pretty sure that's the problem and at least now I can start the car whenever I need to!!!

[ColinP]

Errol,

I think the intention is to measure the resistance of the lead to show that it's continuous - not broken. Don't try holding into 25000v plus (ok, it's low current so it probablywon't kill you......)

This will only work on copper leads. The carbon filament ones are high resistance (cuts down interference). Usuall the HT has no problem jumping little gaps - I remember repairing the carbon HT leads with a pin (stick it into the middle, poush the other half onto it).

Colin

[woo]

Errol,

I hope the problem is solved by the carbon button in the dizzy head. This would prove to be a High Tension problem then. If it doesn't cure it I would endorse Willie's suggestion. Next time the car won't run turn the car over on the starter and see if both terminals remain at 12 volts. If they do, with the engine standing still, put a screwdriver blade, or something, across the points contacts to artifically 'close' them. If the voltage doesn't drop check all the low terminal wiring and contacts between the nut on the points back to the coil terminal. Not forgetting the white block that the coil connects to on the dizzy itself or the integrity of any connectors.

I had an intermittent hesitation while driving just after Christmas. It turned out to be that the wire had got slighly loose in the crimped connector on the coil LT terminal. Everything looked fine. I even took the connector off the coil LT blade to check that it still gripped the coil tightly, but a bump would make the connection and another one would break it. Until when replacing the dizzy head for the nth time, I knocked the LT wire and it eventually fell out leaving the connector still attached to the coil. Fortunately I was doing this at night so the ensuing spark as it earthed against the dynamo pointed out the problem too me