Series 3 runs rough, rich, then stalls

Hello all - this is for a petrol 6-cyl from 1974.
I am aware that there are similar posts as what I am going to write, and I apologise for this. But the advice given there did not do it for me (so far?).
When I start my engine it usually starts fine but runs very rough and stalls after around 30 seconds. The car has been sitting for a while, last time I used it it drove fine at first but then suddenly started acting out and stalled, while driving. I have had a bit of an oil issue with leaky valve seals, so the engine burns quite a bit of oil. But it ran fine, so even though I plan to replace them, I did not consider it super urgent.
My first guess was bad fuel delivery (or bad fuel?), but that did not seem to do it. Can the petrol go bad in the tank? It has been in there for over a year...

Here is what I tested and did:
* Sparks are full of soot. I replaced them, and they turned black again quite soon. I guess this is a symptom of the engine running rich, but I am not sure how to correct.
* Adjusted the point gap in the dizzy - that improved things somewhat, but does not solve the problem. The main thing this did is that I can now rev' it again to high RPM, which was not possible before. Could it be that I improved the gap but that it is still off?
* When I press the accelerator, often times nothing happens, then some times it slowly rev's up but then stalls.
* Fuel flow to the carb looks fine (hence I assume that pump and filter are ok)
* I cleaned the carb and replaced the valve (did nothing for the problem); diaphragm looks fine, as does the needle.
* Air intake looks fine, I disconnected from the oil filter (to be sure), the butterfly valve in the carb opens fine.

I have not replaced the coil - but this (together with the points) would be the next thing I try. Is this a reasonable approach or is there an easier fix that I can do without waiting for stuff to be shipped...?

Thanks!

Could very well be an ignition problem resulting in a miss fire and then unburnt fuel exits. What carb? ?

tottot said:

Could very well be an ignition problem resulting in a miss fire and then unburnt fuel exits. What carb? ?

Click to expand...

A stromberg
I found that I still had new points and fitted them - again a slight improvement, but overall the problem remains.

Have you checked the carb? Oil in the damper is first. Then it may be diaphragm or float issues

can old fuel be an issue? do the flammable components evaporate over time and render the fuel bad?

Do not know what sort of petrol's are to be had in Switzerland but modern fuels tend to go off faster. Also some modern fuels are not kind to rubber components of old. It is not so much the flammability, old fuel will still burn, but the point of ignition "flash point" can change. Try some fresh can't hurt.

yes, that was my thinking - the more volatile stuff evaporates, which would lead to a higher flash-point. Will try that.
thanks for your help!

kyamon said:

Hello all - this is for a petrol 6-cyl from 1974.
I am aware that there are similar posts as what I am going to write, and I apologise for this. But the advice given there did not do it for me (so far?).
When I start my engine it usually starts fine but runs very rough and stalls after around 30 seconds. The car has been sitting for a while, last time I used it it drove fine at first but then suddenly started acting out and stalled, while driving. I have had a bit of an oil issue with leaky valve seals, so the engine burns quite a bit of oil. But it ran fine, so even though I plan to replace them, I did not consider it super urgent.
My first guess was bad fuel delivery (or bad fuel?), but that did not seem to do it. Can the petrol go bad in the tank? It has been in there for over a year...

Here is what I tested and did:
* Sparks are full of soot. I replaced them, and they turned black again quite soon. I guess this is a symptom of the engine running rich, but I am not sure how to correct.
* Adjusted the point gap in the dizzy - that improved things somewhat, but does not solve the problem. The main thing this did is that I can now rev' it again to high RPM, which was not possible before. Could it be that I improved the gap but that it is still off?
* When I press the accelerator, often times nothing happens, then some times it slowly rev's up but then stalls.
* Fuel flow to the carb looks fine (hence I assume that pump and filter are ok)
* I cleaned the carb and replaced the valve (did nothing for the problem); diaphragm looks fine, as does the needle.
* Air intake looks fine, I disconnected from the oil filter (to be sure), the butterfly valve in the carb opens fine.

I have not replaced the coil - but this (together with the points) would be the next thing I try. Is this a reasonable approach or is there an easier fix that I can do without waiting for stuff to be shipped...?

Thanks!

Click to expand...

Well worth trying some new fuel.
And when you have put the new fuel in, try having a play with the timing.
Modern fuel is different to the old stuff, over here, anyway, and I assume in Switzerland as well. I don't find ignition timing to the marks works very well now, maybe as a rough guide, but the final movements of the distributor are best done by ear, and the seat of the pants dynamometer on the move.

Check that carb.