Folks, your mechanical wisdom is required here. That I am at a loss with
explanations doesn't bother me - the work on the carb being the first
serious thing on a mechanical part of my Mk I - but that my mechanic who
works on all the Tigers in our club is also helpless makes me worry. What's
the matter?
After having detected a leaking seal on the accelarting pump I decided that
it was time that I made a start in getting to know my car a bit closer. So I
ordererd a carburator overhauling set and ventured to replace the seals etc.
on my own. It all worked well (seemingly): I took the carb horn and the main
body off, cleaned all the parts, replaced the old power valve (I didn't
replace the fuel inlet needle though and I left the throttle plates and the
throttle shaft untouched), put new seals in and fixed everything again. Now
the big question: Would it start again? Indeed it did. However I had
problems when adjusting the idle speed. The rpm would raise and go down
again, all being unstable. Moreover the mixture obviously was rich, very
rich to say the least. Black smoke from the exhaust! After fiddling a bit on
the idle adjusting needles which showed little effect I was still not much
embarrassed: Well that's a mechanics job then, I said to myself and took the
car to him.
I am embarrassed now: We couldn't do the job. We tried "everything" (that's
what one always thinks). The amazing discovery: Even with the idle adjusting
needles fully turned in the engine was still running with black smoke and
with an amount of CO twice as high as normal. The needles are not worn.
They're o.k. But turning them has no effect at all. We tried different fuel
levels, starting from the "official" one, all to no avail. May be that with
a ridicully low fuel level the rpm was more stable but still the mixture was
EXTREMELY RICH. The fuel inlet needle works fine. The carb doesn't overflow.
The accelerating pump works also fine, the seal is tight, the engine reacts
quickly on acceleration. So the thing which caused me to start the job is
o.k.. All holes or passages seem to be clean. In fact too clean perhaps,
because through some - unknown - passage the excess fuel must come. What is
also different as compared with the situation prior to me working on the
carb. Formerly I didn't hear the fuel pump when it was at work. I only heard
it "click" when it filled the fuel bowl prior to starting the engine. Now
one hears the pump "clicking" even while the engine is running. May be a
sign for the great amount of fuel which passes through the carb right now,
but in itself not alarming probably.
Does anyone have an idea what the cause for this "overrich" mixture could
be? Or: May be that you can give me an indication as to how I could detect
the failure more systematically than just taking all apart once more?
Thanks a lot!
Roland
B 9471941
in Switzerland
e-mail: roland.flueeler@cantrade.ch
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