Aircooled VW South Africa

it has the correct coil,
Im going to lay new wire to coil and see what happens, this car has evidence of past electrical fire, My suspicion is that the
power supply to coil has a intermittent short

I temporarily laid a wire directly to the coil with an inline switch, problem persists.
I feels as if current is intermittently turned off while driving, but not long enough for motor to cut out.
Could it be the fuel cut off valve in the carb intermittently shutting off fuel supply?

fitted working fuel shut off valve with no change, going to switch carbs to see if it helps

fitted working fuel shut off valve with no change, going to switch carbs to see if it helps

Why not connect a 12 v bulb to your coil supply wire and see if it is Power supply,

may be something else like bad earth cable to the engine via the gearbox earth strap.

Maybe spark plugs, have had that happen a lot with champion plugs.

Also had a problem with the coil not being earthed to the fan housing, this too can give you problems specially if its powder coated.

This sounds more like an earth problem, and that is hard to find, only thing to do is remove all parts needing earth, clean both surfaces and refit with paint piercing washers (little star serrated washers)

Replace earth strap with new one and clean all contact surfaces with sand paper before fixing.

Good luck

Herman

since when is the coil earthed to the fan housing?
Power goes in, wire goes to points and gets earthed through the dizzy.


John, I've got stock of the new G-Tech electronic ignition units if you want to try this route.
G-Tech R850, coil R725, you can easily fit it yourself

Tony Z wrote: ↑Mon Dec 10, 2018 7:36 am since when is the coil earthed to the fan housing?
Power goes in, wire goes to points and gets earthed through the dizzy.


John, I've got stock of the new G-Tech electronic ignition units if you want to try this route.
G-Tech R850, coil R725, you can easily fit it yourself

The tin can is earthed to make the high output circuit complete, You can not have a one wire coil, electricity needs to flow from one pole to the next, and if its ONLY connected to the low voltage side with out good earth you will blow your points, and condenser.

Thats why Bosch has made there tin plated with blue sticker, and not fully painted as before. That goes for the bracket as well.

OMO

Herman

The high tension secondary winding's other side is connected internally to the primary. Casing is insulated.
Just confirmed that by measuring a few original Bosch coils.

Dawie wrote: ↑Mon Dec 10, 2018 11:06 am The high tension secondary winding's other side is connected internally to the primary. Casing is insulated.
Just confirmed that by measuring a few original Bosch coils.

Thanks Dawie,

Sorry Tony,

that shows you can not except everything you read ,

never opened a coil before, maybe I should one day

Also explains why it does so much issues when faulty earth is on the engine.

Herman

Herman you never stop learning.I am on here nearly every day and learn something new just about every day but thats because I know about VW even though I am a Diesel Mechanic by Trade I thought it would be easy to work on a Beetle but life is full of surprises I suppose. Thats what people seem to forget they are learning from here and its not just a social site it has a wealth of knowledgeable people here that help so may VW lovers become more involved in doing the jobs themselves that they would have to send out and they are now getting more enjoyment out of their hobby.I mean take FIG Dawie Tony Sean just a few that are like computers without a screens full of knowledge and inspiration. Now I have bored the out of may you have a good week.

retrovan wrote: ↑Sun Dec 09, 2018 11:42 am Why not connect a 12 v bulb to your coil supply wire and see if it is Power supply,

may be something else like bad earth cable to the engine via the gearbox earth strap.

Maybe spark plugs, have had that happen a lot with champion plugs.

Also had a problem with the coil not being earthed to the fan housing, this too can give you problems specially if its powder coated.

This sounds more like an earth problem, and that is hard to find, only thing to do is remove all parts needing earth, clean both surfaces and refit with paint piercing washers (little star serrated washers)

Replace earth strap with new one and clean all contact surfaces with sand paper before fixing.

Good luck

Herman

done all the above and replaced carb and the problem persists

would a cracked head have these symptoms?

No cracked heads, removed inlet manifold replace metal gaskets, now runs beautifully for about 15min, then same engine miss.
I let the motor cool repeated the process 3 times, same symptoms every time. At least its now only happening when the motor is hot (not overheating)
where as before it was also happening when cold, could vapour lock cause this?

I think you have found it, it would seem its to do with the heads.

Maybe your barrels are not sealing on to your heads.

Are you setting the torque correct on the head bolts?

Or your valves are not sealing properly, could also be that your valve setting is incorrect

Are you setting your valves when cold?

When you removed your heads, did you have black marks on the outside top of the barrels ?

Maybe @Tony Z should come in here.....

Herman

I did not remove the heads, I just checked for cracking at the inlet manifold, I assumed it had a vacuum leak caused by a crack that opened up when the motor was hot, valves are set correctly (cold motor)
I'm trying to avoid removing the motor, but I might have to