I've been slogging through the smog check nightmare for a while,
so I just had to chime in...
On Mon, 14 Jun 1999, Atwell Haines wrote:
>
> At 08:09 AM 6/14/99 -0700, you wrote:
>
> Can't say. I know that mine goes put-put-put with the pump disconnected.
> I think the check valve's purpose is to prevent hot exhaust gases from
> ruining the pump itself.
That's in line with the 'official' Repair Operation Manual claim:
"Check Valve: The check valve is a one-way valve positioned between the
diverter and relief valve and the air manifold. Its purpose is to protect
the pump from back-flow of exhaust gases. The valve closes if the pump
pressure falls while the engine is running, should, for example, the dreve
belt break." It also mentions that the relief valve is integral to the
pump on later models.
> >
> >How could the catalytic converter be the cause of the
> >problem? Restricted flow?
>
> I think so. (I don't claim to be an expert here.) When a carb runs rich the
> Cat overheats and literally 'melts' down into a lump. Instead of flowing
> the exhaust through it, it blocks the gassy, hot mixture & it ignites.
>
I'm not sure it 'melts' down. Having just had the unfortunate
chance to look at a failed Spit cat, it looks like a unmelted honey comb
ceramic matrix crumbled into a pile of broken bits inside the can. No
signs of melting, just shattering (this is on my 1980 Spit -- I replaced
the manifold to get ready for a smog check and noticed my dead converter
in the process:( ).
There is a lot to this emissions garbage I'm finding. I think the
gulp valve is being confused with the diverter valve in some of the
anti-backfiring discussions, but I'm not following close enough to dare
try to correct anyone :) (the gulp apparently gives a shot of air into
the intake during sudden deceleration -- luckily, my '80 has the direct to
manifold connection rather than the air rail w/ gulp valve *and* the
diverter/check valve integral to the air pump so I don't have to worry
about all the bits)(at least that's what I'll claim at the smog check
station, now if only my cat was actually working I'd be set).
A final note on catalytic converters, I checked with an exhaust
shop today and they couldn't do anything with the Spit converter since all
their custom or generic converters are for welding into a straight pipe.
The way the Spitfire cat is also the flange that mates to the manifold
seems to make it hard to kludge with a generic replacement (bummer, since
the generic is $100 vs. $300 for a Spitfire one).
John Weale
1980 "British Racing Orange" Spitfire
---======================== John Weale(tyre@u.washington.edu) ==========---
The world does revolve around engineers... they pick the coordinate system.
|