A challenge!

[CapnJon]

I hereby challenge anyone to diagnose the problem! 1964 1200cc 40 hp.

Just converted from 6 to 12 volt. Problem started before I did the conversion. Car was sitting for at least a year, maybe more. Now it starts right up and runs very strong. Just had shade tree VW mechanic (he only works on classic VW's) spend three hours trying to figure this out and he's stumped too.

It will run fine, idle for an hour, no problem. Drive it for a mile or so, no problem. Then when driving, just cuts out. Sometimes it starts instantly (especially with the new 12 volt battery, alternator & coil.). Sometimes it takes 30 seconds and it will fire up. Sometimes I can drive another three or four miles, sometimes it will splutter again immediately or it will drive another mile or two, sometimes less, then die again There is no rhyme nor reason. It's not logical, it's like there's a demon in the car.

Here's what's been done:

Fuel system: Tank drained and flushed. Six fuel filters replaced until they ran clear. Fuel pump working and clear fuel filter near carb always at least half full. Solex 28 replaced with professionally rebuilt (Volkzbitz) Solex 30.

Electrical: New 12-volt battery, new 55-amp alternator, new Bosch coil. Original distributor in good working condition. New distributor cap, points, rotor, plugs. Tested the condenser and it's not grounded internally, so it should be good. Tested the coil spark and it's strong, blue and will jump a 1/4” gap no problem.

Valves are adjusted. When it runs, it sounds sweet and has plenty of power.

Took “mechanic” out for a drive, it died within half a mile. He adjusted the timing. Started right up, drove great for a mile, big smiles all around, then crapped out again. Two more test drives, same thing.
Mechanic has given up. Wife says sell the bloody thing! Help!!!

[Joe vw]

6volt cars are notorious for wire corrosion and brittle and cracked terminals.
It sounds electrical to me. Clean all battery terminals, connections and transmission ground strap.
temporarily run a wire from battery positive to the positive side of the coil, see if it still stalls out.
I suspect the ignition switch circuit.

[CapnJon]

Thanks Joe. Just replaced complete ignition switch. That's not it. The problem is that it's so random!

[CapnJon]

I give up today! Tomorrow I'm going to inspect every single wire and connection

[Bonemaro]

Vaporlock?

[CapnJon]

Hmm! That's a word I haven't heard in many, many years! How would I determine if that's the cause?

[Bonemaro]

Are your fuel lines close to the engine? Sounds like this is happening once everything heats up. I'd be interested to see what your fuel pressure is doing when it dies.

[CapnJon]

Not any closer than they need to be! I'm going to be interested too...i will certainly post results of whatever I discover as this progresses. Thanks for your response...

[SCOTTRODS]

Can be : Fuel Pump issue, could be the pump shaft sticking once warm.... Solution, Pull pump, shaft and phenolic piece, run fine emery cloth or similar down the bore of the Phenolic guide to insure enough clearance the rod does not bind up once warmed up.

Can Be: Bad Ground to Chassis..... This one will be the Ground strap usually, between the Trans and the body, up around the nose cone of the trans.... The whole thing is a Braided wire mesh style ground, and it will internally corrode terribly to a point that it can cause this kind of symptom.

Possible cause : Wrong coil..... just a shot in the dark there, or maybe intermittent coil.... Not nearly as likely as the other 2 suggestions.

Those are my suggestions..... Let us know.

[CapnJon]

Thank you for taking the time to respond in such detail. All helpful, logical suggestions. This week will be "find the problem" week! First I'll determine if it is a fuel or electric issue. Then examine every component. Them drink some beer. And then get back to work on my third book

[Ol'fogasaurus]

Never assume on the condenser! If you do the points then do the condenser. One of the condenser's jobs is to start and cut off the spark crisply and give life to the points. I have seen them weak/bad but still check out good. Just a thought.

[CapnJon]

Right - good thought, thanks. I'll get a new condenser tomorrow (if I can find one in St. Augustine!).

[goober]

Gas tank vented properly? Could be vacuum building in tank.

[CapnJon]

Thanks - fuel supply seems to be fine. Tomorrow I do some serious electrical testing...

[CapnJon]

Didn't have much time today, but I eliminated two easy solutions...Ran a wire directly from the battery + to coil+. Ran great for two miles, then, dammit, died on me. Started up after ten seconds and got me home. Put on new battery ground strap. Still dying! Tomorrow, new condenser (don't think that will help) and when it dies again, will remove top half of carb to see how much fuel is in float bowl...