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Re: [T3] Not quite there yet (addendum)



> DanielB=> What can actually cause a carb to leak
> => gas into the cylinders?
>
> I think the most common cause is a fault in the anti-siphoning system
> represented by your electromagnetic cutoff jets. After that comes stuck
> float needle valves and screwed-up floats (never, ever try to 'adjust' a
> float on a PDSIT!). Carbs and throttles usually leak air rather than fuel.
>

Neither of my carbs has the cut-off valves, but a screw in pilot jet
instead. I have no idea why this is. Someone once said (on the Type 34 list
I think) that this may have been standard in our climate, but every Beetle
that I have seen does have them. Anyway, if you think this could be causing
what seems to be a very large leak, the obviously I'll get some cut-off
valves.

> I have to think that given the amount of time you've actually had the car
> running, a carb leak of sufficient magnitude to give you a problem would
be
> alarmingly obvious. And it would run terrible, if at all.

This has been puzzling me too. The car doesn't run badly, and it doesn't
smoke. It does have the problem that I've been trying to deal with recently,
and it is true that my carbs are not perfect and still need some attention,
but I just can't see where they can be leaking so much. When I had them out
I tried filling and overfilling the bowls, and messing with them in various
ways, and I couldn't see any petrol coming out of anywhere unexpected.

>
> => how can I test the fuel pump?
>
> If indeed you do have a lot of fuel in your oil, this is the more likely
> source, imho. To be sure you have to tear down the pump and examine the
> diaphragm closely for holes. It's pretty straightforward.

My fuel pump is a Brosol knock-off, which doesn't take apart. I'd VERY much
like to get my hands on one of the original VW fuel pumps with the plastic
cover, if anyone has one.

> I'd like to be able to quantify this problem more clearly: When you did
the
> carefully measured oil change, did you notice whether the case was
overfull
> to start with? After you changed the oil, about how much did you drain out
> again, and after how much time?

I can't be too exact as of now. At the weekend, if it's not raining, I'm
going to drain off the rest of the oil and measure it.  I think it is
currently slightly lower than full, assuming the dipstick is accurate. I
drained off somewhere in the region of a litre, I think, which means it was
perhaps 700-800 ml over. I last changed the oil on the 21st of August. It is
possible I suppose that my old carbs were leaking. I removed them sometime
in mid-September. I don't remember noticing that the oil level was too high
after the oil change. Anyway, I'll know more at the weekend.

Thanks,

Daniel Baum
1969 Type 34 automatic
http://www.qldesign.com/type34


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