Ignition question

[wuvvum]

Here's a question for anyone more mechanically minded than me (so that's most people then).I've been fighting the ignition system of my Austin Ten for a while now. I just can't get a spark, despite the fact that it was running fine when my mate had it (I saw and heard it running on more than one occasion) and none of the ignition bits had been tampered with.Bear in mind that the car is positive earth, which confuses the feck out of me for a start.First oddity was that the live feed from the ignition became an earth when the ignition was switched off, which seemed odd to me, unless the ignition switch earths the coil to switch it off rather than just breaking the circuit? For the purposes of testing though, I just ran a live straight from the battery live (-) terminal into the - side of the coil, and then took a wire from the + side of the coil down to the distributor.The live feed from the coil feeds into the mobile point. The points are opening and closing as they should, and the mobile point is live when the ignition is on; the static point becomes live when the points are closed, so current is obviously getting through the points. I would have thought though that the static point should be earthed somewhere along the line in order to complete the circuit, and it isn't - run the tester from the live battery terminal to the point and it's completely dead. The only thing in the distributor that is earthed is the outer body of the condenser.The other thing that doesn't seem right is that both low tension terminals on the coil are showing live all the time - I thought that the earth side of the coil should only have current passing through it when the points are closed.So basically, the points aren't breaking the low tension circuit in the coil so the high tension windings aren't energising - if my understanding of the workings of a coil is correct. The problem is that there is no circuit as such through the points because there's no earth there, so technically it's as if the points were permanently open so the earth side of the coil should be permanently dead, shouldn't it? I've tried wiring the coil up the other way round and it does exactly the same thing. It's the coil off the Skoda so I know it's a good 'un. Any ideas would be greatly appreciated...

[Des]

Sounds like the baseplate, the part that the points mount on, isn't earthing to distributor body, possibly a braided earth lead that should join the two is no more.

[wuvvum]

Right. So in theory if I run a short wire from the fixed point to the screw that holds the condenser in (which is earthing fine) that should sort that bit of the problem? Would that also then sort the issue of the earth side of the coil being permanently live? For some reason I still have a complete mental blockage when it comes to positive earth electrics...

[Station]

Positive earth has the positive of the battery connected to the ground. I'd imagine the ignition components are wired in series on the negative to complete the circuit? It's identical in theory to negative earth, a bit confusing like. Just remember the electricity is ALWAYS trying to get to the earth, ie. the car's body frame. Part of you ignition circuit could be doing this by a back wire, or a perished earthing cable.

 

I replaced all earths on my Starion, and it ran 'beautifully' (if it didn't have fuelling issues), and is something that is missed by nearly everyone. First thing you should do before anything is do this, get some multistrand earth cable from Maplin, and clean up all earth points! Remember, electricity travels on the OUTSIDE of a conductor (like the copper wire), so is going to get obstructed by corrosion, or a rusty earthing point.

 

Old vs New:

 

 

Do it!!

[Des]

Yes, that should do, once the points are closed, you shouldn't get any voltage reading on the low tension from the coil, a quick way to check things, pull the coil high tension lead from the dissy cap, and place the end close to the rocker cover, about a 1/4 inch, then check the points are closed, turn on ignition, push points open with screwdriver, (insulated handle), you should see a nice spark from HT lead, and a bit at the points, if not, poke the screwdriver between dissy body and points terminal, if it sparks now you've no continuity from points to distributor.If you have spark from coil, but still no go, hold the coil HT lead to the rotor arm centre and repeat above, you should see no (or virtually no) spark here, as long as the rotors insulation is ok.

[wuvvum]

OK, I'll give that a try tomorrow. I might just run a wire straight from the point to the battery earth for testing purposes, that should eliminate any doubt. Obviously I'll have to come up with something a bit better if it does work. Cheers for your help gang.

[Andrew353w]

+1 /\The only extra comment I'd add to the wealth of Autoshite information already given is this:When you wire the points and the coil directly from the battery you'll eliminate any problems in the car's wiring and switching. Might I make a few extra suggestions? Connect one end of the H.T. lead to the coil, connect the other end to a spark plug and rest the spark plug on the engine block. When you open the points, using an insulated screwdriver, as you SHOULD see a fat spark at the plug and a small one (or none at all) at the points. If you see a fat spark at the points and none at the plug, aside from all the suggestions already given, one more could be a failed or knackered condenser. There's only one way to confirm this and that is by substitution. Hope this helps! Good to see the Autoshite Team assisting on this one!

[wuvvum]

a failed or knackered condenser.

Hmm, I hope not - somehow I think walking into Wilcos and asking for a condenser for a 1945 Austin Ten is going to be met with blank looks...

[daverapid]

Remember that if you're using a Skoda coil it's ballasted down to 9 volts...or are you bypassing the ballast resistor?

[Andrew353w]

a failed or knackered condenser.

Hmm, I hope not - somehow I think walking into Wilcos and asking for a condenser for a 1945 Austin Ten is going to be met with blank looks...

Oops! Forgot to read all the thread! Did they have condensers? Suppose they must have! Any 30 micropharad capacitor normally serves, though!

[wuvvum]

Yep, they did have condensers, but they were a bit of an odd design with a screw thread on the terminal rather than a wire soldered on like most condensers have. Would be bloody awkward to adapt a "normal" condenser too, as it's all a bit tight in there. Anyway, the good news is that the condenser appears to be fine. I made a (very) temporary earth up using a bit of thick copper wire clamped under the condenser retaining screw and then sort of bent into a spring to press against the static point - seems to have worked though as I shoved a spark plug into the coil lead and got a lovely fat spark. The car won't quite start yet, but it is firing - it's got one of those stupid old starter motors that throws itself out of mesh as soon as the engine even hints at firing - if it had a proper pre-engaged starter I reckon it'd be running by now. It chomps through batteries at a rate of knots as well, and I've lost my jump leads. Still, now that it's sparking that's half the battle - thanks for the help peeps.

[nigel bickle]

Tip fuel straight down the carb-that'll get it going.My '39 Standard Flying Nine suffers similarly. I overhauled the iginition system to get a fat spark- but the pump is pretty weak -despite several attempts to overhaul. A cup of petrol gets it started -then the pump takes over..Long term answer is a (pos earth 6v) elec fuel pump- but they're a bit pricy for now. One day...