Irritating Points Ignition Failiure - a bit stumped!

Have you checked the cams are turning? it is about 40 years since I changed one, but iirc there are two chains, one runs the cams, one runs the jack shaft for the oil pump and distributor BICBW and I cba to look it up.

Be careful with that s*it...I managed to blow the exhaust manifold off an Audi A6 once with a 'good dose'.

I've not looked but it's easy enough to see the exhaust cam through the oil filler.

Although, I'd have thought if the cams weren't turning the engine wouldn't either - or at least it'd be making very expensive noises if it were.

When it cut out it did just that, there weren't engine failing noises.

It's not something I use to start cars often but it is useful to find out if there's a spark. Or not, as maybe the case.

They look fine.

Duh! LMP!

Take the plugs out, connect them to the leads and wedge them against the engine metalwork so you can see the spark gaps. (Several mole grips, perhaps?)

Crank the engine. You should see a sequence of nice blue sparks in sequence at each plug gap. Easily loud enough to hear over the noise of the engine cranking.

Also you should be able to smell petrol vapour being pumped out of the plug holes - that should confirm valve and carburetter function.

You can .. as a bit of a bodge, run a bit of light thin wire from where each lead starts along its length around the outer of the plug lead, bit of tape to hold it in place to each plug top should work OK make sure its all up in the air and not touching anything metallic and keep well away from same;!. That will bypass the lead..

That is more or less how plug leads were many years ago before radio suppression was thought of> If that makes it all that better then new set of leads..

The more I read about this problem and the suddenness of how it came about it seems to me that this isn't the problem 'tho, it does seem perhaps that the timing has gone to c*ck somehow. If you are getting some sparks albeit not very good ones they may well be sufficient to run the car if all else is as it ought be.

I presume that the car was running and starting well before this breakdown on the road?.

If so can you check the timing either by turning the engine over by hand made easier by removing the plugs and see if when the timing mark is in the right place on a given cylinder does the spark occur at the right place?.

If you can't do that then a slightly cruder way is to very slowly gently turn the engine over by hand or in gear and moving the car if you can and place a rod of some light metal or similar to feel when the piston is approaching top centre on one part of 2 revolutions you should get a spark at just a fraction before its top dead centre movement.

Presume also that the plugs are by now getting a bit of petrol on them as well proving that it might not be a fuel problem?..

And have you done a compression test at all?..

Yes, I've just come across this thread and came to the same conclusion that a slip of timing is the likely reason.

Valve timing is probably okay but perhaps something in the distributor drive has sheared? Have you checked the dwell angle?

Tim

It won't run - I know no other way to test the dwell.

Ok. Does slipped timing explain the lack of decent spark?

you can set dwell spinning it on the starter.

No.

You actually expect people to take the symptoms into account when coming up with a diagnosis?

When was the last time you observed a good spark at the plugs?

If you don't know exactly how good / bad the spark was / should be, it may be something else.

Is the fuel pump running? If it's a diaphragm type is the diaphragm split? Engine mounted mech pumps tend to dump fuel in the oil.

Can do, if the rotor arm doesn't line up with the dizzy cap anymore

Yes. There is fuel under pressure at the banjo after the fuel filter/bowl.

It's an SU electric type.