Club 80-90 Forums

just re built the engine and i want to get it running as best i can before i take it to my local VW wizard to fine tune it.
It is running on 3 cyls when cold and no. 3 cyl on seems to start when its hot! i know this cos the exh pipe is stone cold for a spell.
i have noticed as well though that the vacuum balance pipe that runs between the two carbs is getting very cold and wet through with condensation on the outside. My experience tells me this is due to a rush of a vacuum through it but it aint obviosly right.
Any ideas would be appreciated ta

If its a balance pipe there shouldn't be much if any real flow through it under normal running, it balances pressures not flow.

But if its not running on one cylinder then it will, and being small-bore the speeds will be high, chilling it. Surely the first thing is to get the engine running on 4 cylinders at all times?

i'm working on that assuming the same that this is the cause.
i have agood spark so i cannot see why trhis is happening as the 4th appears ok.
i can only think valves and will try and check these before i am compelled to get the barbie out (oh wow)

The good spark might be OK at atmospheric pressure, are you sure (engien analyser) that its sparking when running in the cylinder.
Valve clearances?

how do i know if there is a park in the cyl.
what valve clearnces my books say to touch the push rod and wind on 2 1/2 turns when a TDC they are hydraulic

engine analyser, sun tuner type of thing whetever they're called today
One dodgy HT lead or plug is all it takes

Just check your compressions first, that will square that one away... then move on, if there's fuel in the cylinder and a reasonable spark and compression it will fire.

Sounds sparks to me but thats speculation without doing a few tests..

e.g. you might swap the lead from the duff cylinder to the good one on that side and see what happens?

If this is a first run since building the engine have you got the dizzie in the right position, seem to remember its possible to get it runing with it either 90 or 180 degrees out...

comp is in order i would expect cos i have new cyls and pistons etc. i did have the dizzy in wrong but that is now correct. i will try the plug leads swap tomorrow

If that doesn't work, or give a pointer, whip the plugs out on the duff side and puttting finger over plug holes in turn, spin it over and see if they seem the same - assuming you haven't a compression tester gauge.

That should remove that option... then think dizzie cap maybe.

think i have sorted it. comp does not come in to question as i have new cylinders and pistons etc.
it appears to have been the plug lead. i couldn't swap them about because of the lenghts etc not reaching
when i looked at the dist end the connection was relying on a brass crimp with a spike for want of a better term that should penetrate the insulation and contact with the center core, so to make double sure it was touching i stripped the ins back and folded the center core back on itself and replaced the crimp.
The vacuum tube i was on about is still cold but doesn't seem as bad. hoping a tune up will sort that and the strong smell of fuel in the exhaust fumes

Good stuff.

Now run it in with plenty of full throttle bursts, extending for longer and longer as the miles go by to get the rings to seal properly