Ok, so I know that diagnosing issues over the internet without poking is very hard, but let me tell you the story, and see what you think.

My 66 (1300) engine has been not starting for ages now. Luckly I only drive it to the train station and back, and I can roll start it at each end. It kinda goes 'wump wump',but doesn't turn over enough to acheive anything.

Fact 2. Not sure if this is related but...I have a very rusty rear taillight and blinker, and the indicator was earthing through the brake light, and making it blink, until I managed to wriggle it to get contact (I know I need to fix this right..)

fact 3 It started to rain, and about that time, the engine started starting OK...so Is it possible that the wet made the icontact better, and so it started better? (note: 6V)

fact 4: tonight, It was turning over OK (still raining), but wouldn't start. (even when rolled ) i got the NRMA to jump start (12V on 6V..ouch!) and it finally started, but it then coughed and spluttered a lot, and wouldn't accellerate much. i am yet to see if it goes in the morning, or If I need to get my wife out of bed to drive me...

I also suspect that the petrol filter needs changing, and I have a new battery on order.

Discuss.

sounds like my 61 was. it would turn over then just about stop and not start.Changed the dizzy to a 009 now starts easily. Found rotor button was missing the steel locating part so I think it may have been spinning on the shaft and making timing way out:o

Yay....I got it! (Ok I am a new mechanic.....)

I ordered a whole bunch of things (fuel filter, spark plugs, generator brushes, fresh air tubes, tail light replacement (not all for this, but some just to double up on the delivery).

I decided to move the not working bug into my garage so that I can work on it at night. This involves going down the driveway, and I ran into a post, and couldnt drive forward. Man handled the car sideways (luck it is a small car!) and got it parked. SOmewhere in this I pulled the hand brake too tight, and pulld it off the top of its ratchet (now I have no brake and no forward motion!). Fixed the brake, got it parked, decided to have a little fiddle...

and there was a little bit of fluff on the rotor! removed, car starts nicely!

I will do the other stuff anyway....It should make it feel a little happier

another interesting thing. It started ok in the garage, letf it running for a bit to charge the battery, parked it out on the street again (I can roll start from there..I dont trust it yet! ) and stopped. tried to start again straight away, and it didn't (would only turn over once or twice..and VERY slowly). Came to try to start it this morning, and it starts! WTF?

removes and clean (with a wire brush) the terminals on your battery, earth strap to pan, starter motor and engien/gearbox earth. Sound iek too much power is being 'lost' between the battery and teh engine.

And do an oil change!:kiss

when it is difficult to start, is it parked on a lean to the left (most likely, or a leak to the right) it is endemic VW problem that fuel can leak down to & stay in ) 2 of the cylinders thereby causing hydralic compression (almost wont turn over) & totally flooding 2 spark plugs ( difficult to start on only 2 cylinders & ragged running for a short time

maybe a little to the right. left wheels about 20cm higher. There is a bit of a slope down at the back too (though not enough for the car to actually roll)

It can help to rig up a cable directly from battery to starter, so that the power doesnt need to run all the way from the battery, through the ignition switch and back down to the starter. You need to rig up a switch which is located down near the battery but operated from the ignition, that allows the current to run down the new direct cable.
I did this and it solved all my starting problems.
John Muirs book has a bit of a description of this kind of thing

Pull your tank out when its almost empty and clean all the crap out its an easy job,i was goin through a filter a week till i did