DDK - Die Deutschen Klassiker

So,

Bit of a strange one.i’ve been having a bit of a problem with the 356 recently.

The other week, I took it to London and it drove fine, although seemed to judder, under what I assume was a mid-fire when the car was under load.

Car then broke down in the middle of the A3 when coming to a standstill in traffic. Had to push it across three lanes and off the A3 at the Robin Hood roundabout.


Car then after a bit of amateur fettling, started, but was rough as a bears arse- and seemed to only be running on 2 cylinders…

Nursed it much of the way home / it died again- left it for 30 mins and then it started, drove perfectly well…. Got the car home and changed the distributor cap, thought that the main point line in was dodgy. Tried the car out, all seemed fine…


Was due to go to the Fairmile yesterday. - Car started, no problems, drove well under load, so took it on the motorway.

Same thing happened again, although this time no warning signs under load. - came off the M25 to the A3 ( now I have PTSD of the A3) and it just died.

Wouldn’t start, but kind of catches… almost as if there’s not enough petrol getting to it….

4 hours later the car was recovered back to mine.


So a bit of a weird one… anyone got any ideas where I should be looking?

Fuel, coil, condenser ?

Cheers!

Disco

is there fuel in the carb bowls ?

Are your carbs Zenith 32 NDIX ?

Regards
Mike

Coil overheating
Condenser failing
Points gap..............has the heel on the point where it touches the cam lobe worn down?
You can check the fuel delivery by getting someone to help you turn over the ignition, whilst you disconnect the fuel line going into the carb, and put that in a jam jar, and see it is actually pumping fuel.

Stuck float in the carb, crap in the carb.
All the basic stuff really definately sounds fuel or ignition related.

I think something is warming up and separating? I would replace coil, condenser, points, rotor arm and plugs. Check all the connection points on the coil and condenser. Check ignition wires for cracks?

Maybe something is heating up the petrol? Are the lines all away from hot areas? Any chance a fuel filter is metal and heating up. Carbs getting hot and fuel is evaporating?

I'm not sure how to test as seems to only happen after a long hot run?

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Thank you for the pointers - now you mention it I think it could be the fuel evaporating- I took the air filters off and when I manually pushed fuel into the car a it looked like there was vapor … wonder if the fan is working and if not, causing the engine to overheat.

Will investigate …

If none of the checks mentioned already don't work, then try another fuel pump.
This sounds very similar to my experience with my first 356. Would run perfectly well, then once warmed up would die and not re start until left long enough for it to cool down.
Then one broken down day, an AA man came to recover me and said he's seen this in VWs. The pin in the fuel pump is worn just enough so once warmed up it has too much wear and the pushrod action is not enough to pump the diaphragm for sufficient fuel supply.
Luckily I had a spare, put it on the next day and all was fine.

Good luck.

Karl

If you have an electric pump, ignore what I just said.....

Pretty sure it’s mechanical, not electrical. ! Another box to tick off ! Thank you!

Been there with my 356.
Was worst when I’d stopped for say five minutes but less than half an hour.
Diagnosed it as fuel evaporation, the 6v starter struggled to wind over fast enough to push it through
I initially solved it by plumbing a priming bulb into the fuel line just before the fuel pump, I could overcome the “air lock” in the pipes caused by evaporation of the modern fuel.
Eventually I fitted a little electric 6v pump under the wooden passenger footrest.
I had a spare hole in the dash and a redundant warning light from a long gone accessory.
This solution is far more civilised and offers the added bonus of a prime before starting too, saving on those precious cranking amps.
Easy to tell when system is full as the pumps note changes!

The closest I came to this was a failing and then failed condenser (6V). It seemed to be related to how hot the car was, so I would start off fine from cold then struggle to hot start (say after a fuel stop) where it wouldn't fire or lurch a lot under power. Eventually failed totally on the way back from Classic Le Mans after a very hot run down and some playing up on the day before return.

Replacement condenser and also coil and I made it back fine. Thanks to Garage Gilbert in Beaumont sur Sarthe for fixing it in a few hours (including getting a 6 volt condenser biked over).

Let us know how you get on.

The quick fix for vapour lock is a half reverse turn of the crank. Can be done in neutral with a fan belt spanner

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So I thought I’d add a little to this, given all the suggestions so far.

So I do think it has something to do with the carb, or both carbs… what I’m getting is it misfiring in the left hand carb, so I’m getting some soot or similar on the inside of the carb. I know this because I’ve taken off the air filters.

The car starts, begrudgingly when cold, gets up to temp and then the idle dies and I can’t then restart it… very weird.

I also think the carb might be overheating, because when i pushed petrol into it manually, when ‘ off’ its turned to vapour…

Still no closer to fixing it. To be honest, it’s a bit of a dark art, an engine and carbs to me… but I don’t think it’s a coil, is it? Because of the coil failed, it wouldn’t then start at cold ?

Interested in your thoughts on this .. thanks guys for your help and patience !

If you have weber fit these

https://ebay.us/m/i3tlqb

It will stop the heat soaking up into the carb. I'm sure others are available for solex. I had a similar problem with my 914.

Also I find for a hot start foot to the floor makes the car start better.

However, if reluctantly starting when cold too have you checked your timing at idle or your points gap?

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Disco wrote: ↑Wed Jul 16, 2025 12:01 pm I don’t think it’s a coil, is it? Because of the coil failed, it wouldn’t then start at cold ?

Mine would cut out occasionally when driving, could usually jump start it with momentum before it came to a halt. Turned out to be the coil; easy replace to eliminate from your enquiries & no harm in having a spare