Allegro Club International

[brian]

This makes me think that maybe your alternator had blown the electronic ignition unit in the first place????

[Colin T]

The electronic ignition hadn't blown up, according to the supplier it's working fine but just doesn't work fine on my car any more!

My alternator has '14/95' on it's label - week 14 1995? The service history is a bit sparse in the mid 1990s. It looked fairly new when we got the car in 1998 so it makes sense that it was a second replacement (i.e. the car's third alternator). The brushes have plenty of length and the bearing feels fine.

I'll swap the voltage regulator for a new one (they are cheap) and if that doesn't help I'll have it professionally checked out.
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Laurence]

Hi Colin,
I would change the surge protection device in the alternator as well just for good measure if there is any chance that the alternator is affecting the electronic ignition.
Have you had a cylinder pressure test? Worn or broken valve guides could be causing the valves to not seat properly so causing the misfire/rough-running.

The rough-running fault may not be caused by the ignition, cheers, Laurence.

[Colin T]

Hi Laurence, as the problem appears to have started to affect the points/condenser in the same way as the electronic ignition, I will still run with the points/condenser for a little while to see if all is OK, but I'll have a look at prices for surge protection devices. If they are cheap, I might fit a new one for good measure as you suggest. The voltage readings were dropping where the misfiring occurred with the electronic ignition fitted, which I assume is the opposite to a surge problem.

I'll do a compression test once the electrics are sorted, but the misfiring that happened on Monday mirrors the problem with the electronic ignition, so I'd be surprised if anything is amiss with the engine internals. The local garage were happy with their compression readings (whatever they were exactly) and my low readings were probably due to forgetting to open the throttle. BUT I swear that the tappets are noisier than they should be, and I've adjusted the clearances (they weren't really out of adjustment but I redid them anyway).
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Colin T]

I've replaced the voltage regulator, but this hasn't changed the reading from the ammeter:

[Colin T]

I took my car for some diagnostics to be done on Thursday, but not happy with the results.

Basically, it was out of tune - dwell (when I measured it it was only 1 degree out, so within tolerance!), timing (looked to be about 13 degrees before TDC with vacuum disconnected at 1000RPM when I had adjusted it), throttle damper (I had disconnected this at some point and not readjusted), carb piston damper oil (I was using oil that was too thick) and mixture (fair enough, I had richened it as it made the car run better).

However, the car now appears to run worse - it hasn't done the misfire since getting it back but the idle is still uneven, as can be seen with rev counter needle movement and by listening to the sound of the engine. It also feels a bit odd whilst driving - a sort of backwards/forwards motion at higher RPM. I had experienced this before and got rid of it by richening the mixture. I think I can still feel a misfire or unevenness through the car's body.

The bloke who looked at it couldn't suggest anything, other than possible icing of the carburettor due to a couple of splits in the heat chamber/air filter duct (I have taped this up as a temporary fix but it changed nothing, I doubt it would have been the cause) or that the immobilizer could be interfering (I ran the engine with the coil supplied directly from the battery and it still ran rough).

I also tried squirting some WD40 around the throttle spindle and exhaust manifold but I don't think it did much.
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Colin T]

I also tested the battery voltage with the engine running and was getting 14 volts - not sure why I only getting 12 ish before.
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Colin T]

I have measured the voltage at the coil and am not sure it is correct - with the engine running I read 14v at the positive terminal and 6.9v at the negative terminal and at the connection between the negative low tension lead and the black lead going to the condenser.
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Colin T]

I took some more measurements today.

Battery voltage appears to be fine, 12.47v with engine off, 14.12v at fast idle.

With the ignition switched on, points open but engine not running, I was reading 12.40v at the coil + terminal, 12.38v at the coil - terminal and 12.35v at the LT lead/condenser terminal connection.

With the engine running at fast idle, I was reading 13.40v at the coil + terminal, 7.29v at the coil - terminal and 7.28v at the LT lead/condenser terminal connection. These readings got slightly higher with slightly higher RPM, and all read slightly higher with another meter.

Are these figures OK? I assume that the drop of voltage across the coil is correct.

EDIT: - should have mentioned that the coil's primary resistance is 3.7 ohm at somewhat less than 20 degrees C !(Lucas LA12 coil), no ballast resistor present. Could it be this resistance that causes the voltage drop?
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Colin T]

Replaced the coil, made no difference.

Maybe there are no electrical issues now - perhaps the original problem with the electronic ignition was due to the dying battery?

And the later problem, like the original problem but nowhere near as bad, is due to whatever is causing the top end/valve gear noise, as this second problem is similar to the problems I now have with the points and condenser, which probably isn't ignition related as there's nothing left for me to swap over to eliminate - I've eliminated the entire ignition system and the car still runs really badly with a wavering rev counter needle.

The alternator light appears to be behaving itself atm, not sure if it ever misbehaved after I swapped the voltage regulator.

Looks like I'll have to take my car to a third garage ad see if any problem is definitely diagnosed.
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!