Dead...again...Running...oh...sickly

[pyoorkate]

So, Brick's decided to be a brick; rather annoyingly it's happened about half a mile from my house (too far to easily push, too close to get the RAC to it). If I can't get it sorted before Saturday, assuming it's not vandalised; hit by someone; towed away, then the garage will come rescue it (sadly the guy who runs the only garage I trust is currently off sick) but at the moment I need some ideas for what to look at.

It's been running perfectly albeit needing a service - yesterday I changed the alternator (in the dark and rain), started the car a while later (started fine), and headed off down the road. After about 400 yards it stalled and was a bit tricky to restart, and then half a mile down the road it stalled and won't restart.

It'll turn over, and catch but after firing a few times it'll die - and as soon as I let go the starter it'll die. Sometimes it'll stay running for a few seconds if I keep the starter turning...

It did previously have some problems with insufficent voltage getting to the coil when starter was turning (there were some dirty connectors); but I used to get round this by starting the car with a jump lead running to the coil - obviously that's not the issue this time 'cos it's catching but not staying running.

I'm at a bit of a loss really, anyone got any suggestions as to where to start looking? I've had a bit of a nose round this morning (but I'd just come off a night shift and honestly assumed it'd just got really wet while I was changing the alternator and decided to have a strop) and couldn't see anything wrong (apart from the whole not starting thing). I've faintly wiggled connectors, cursed and sworn a lot and stomped off in a mood. None of this seems to have helped

[droopsnoot]

If it has the standard coil setup, couldn't it still be something to do with voltage getting to coil? As I understand it, the coil usually operates on around 6v, but when you're cranking it over a feed from the starter gives it 12v for a short time, until the engine starts running. Because yours runs when you are turning the starter, but stops when you let go, I wonder whether the issue is that it's not getting much (or any) voltage through the normal loom connection?

[shamm]

Yup, it does sound like the connection from the ballast resistor is broken or the solonoid is not connecting it.

[pyoorkate]

See, I thought that, so I bypassed the resistor the same way I used to when the connections were grotty; and it'd still not start with the jumper cable running directly from battery positive to coil positive.

Bizzarely, I went down there today to shove it into the corner of the place where it's stuck, and it started. Unfortunately I was so shocked ('cos I really didn't expect it to start); and wasn't actually sat in the car properly that it stalled and then wouldn't restart.

Argh!

[pyoorkate]

Okay, now I'm replying to myself; a worrying trend...

I went down there this morning armed with my cheapometer and prodded and poked. With the flat battery in the coil was getting 7ish volts on the IGN position. Not *really* enough, but hey. A few goes at turning the key before the battery passed away completely (*sighs*) and I switched back to the proper battery. Again, the car wouldn't start...

Switched the coil for a new one [logic for this is below, but mostly based on 'hell, it's the only real spare I've got in the car'] and suddenly we had running, idling and happyness.

'course, about half way home it started running less well, but it made it to the space outside my house. It sat there and idled 'adequately' for a while, before dying. Having checked - running voltage was 10v (approx) to the (ductaped in) coil. Before dying it started to run on only three cylinders (reving it gently didn't cure this, it was commited to the 3 cylinder idle) before it stalled. It restarted, but still idled on 3 cylinders...

Anyone got any suggestions? The mechanic down the road said 'ballast resistor', but if it *is* that, why's the voltage okay?

[Logic for the coil swap: Well, I've had lots of bizzare faults with failing coils; particularly coils that failed shortly after alternators failed, although none would do what the posit in this case was (good spark on higher voltage, but not on lower). Still, swapping it got me home ]

[lambaj]

I'd try a new condensor too.
If you alternator was on its way out, you can get all sorts of high voltage conditions that strain the electical system. Coils often get bitten as the overvoltage causes insulation breakdown problems. Same can happen to the condensor as it is basically an electrolytic capacitor, and these don't like too many extra volts.....
Also consider your centre HT lead - its been very cold and damp lately and you might have some HT tracking going on.
Also check your fuse box, make sure the ignition fuse is not all corroded and generating some resistance, so dropping the voltage to the ballast/coil feed.
Hope it helps

[pyoorkate]

Thanks for the suggestions...

Ah - should have mentioned - has an electronic ignition system fitted...

- The HT leads all look good (they're fairly new)
- The fuses look clean and not too corroded
- Rotor arm and distributor cap aren't brilliant, but they're not awful either (it's past service time, so they're all due for replacement, but they're not awful)

[lambaj]

There is one thing to consider, if you are using a cheapy digital voltmeter, these only see the average voltage. It is possible that the volts are bouncing up and down as the electronic ignition module asks for a spark. This might explain the 10V you are seeing. 12V most of the time when there is little current flowing, and only a few volts for the fraction of a second the spark is 'live'. If you ignition module runs directly from the + on the coil, this could also me messing the module about. Also need to ensure the ignition module is properly earthed as the resistance point can come in anywhere in the circuit. A corroded earth tag might explain it.

I am assuming that you are using a points triggered system ? or is it a reluctor/magnetic one, or an optical style ?
If you have an original AC delco dissy, then the problem could also be extreme wear in the dissy shaft, causing it to wobble. If you have points, the gap is impossible to set as the shaft flops about (!). This will only not matter to optical setups, as magnetic sensors need an accurate gap as well.

Go with the poor power supply to the coil/ignition module 1st, it still sounds power related to me.

Tony (HA21)

[pyoorkate]

It's an optical triggered one (Lumenition or however it's spelt); and it's an ancient cheap analogue voltmeter. I'd not trust it with my life, but it reads 12 across the battery, and 10 on the coil. Probably more across the battery when the car's running

The dizzy is knackered (someone munged the threads where the points attach, the electronic one doesn't need to be adjusted so once I got it in the right place I've not fiddled with it), but the shaft bit's okay (which is why I switched to electronic ignition ). The earth for the 'lecky ignition seems fine.

The thing that gets me is it was running perfectly before I changed the alternator; I change the alternator, and now it won't stay running for any period of time. Hence my total confusion about what's gone wrong...

[lambaj]

Your luminition will not be happy with only 10V..... but that does not help. Are you sure your alternator is providing a good charge voltage ? I would expect to see a minimum of 13.8V from a healthy alternator, at that would be measured across the battery terminals. Any lower and you looking at a low charging voltage.
It is possible that your new alternator is the cultprit. I would try to measure the voltage when the engine is running (ahem, yes I do realise that might be tricky) Maybe disconnect the alternator and run the car just from the battery for a few minutes. Be careful not to touch the heavy cable to earth as its direct connected to the battery. If it runs, then for what ever reason, the alternator will be the problem. It should not take long to try it.
Tony