>actually, we are both probably correct. since i ahve not heard your
>backfire, i cannot comment on loud vs violent vs a satisfying burble
>_there ain't no such thing as slightly pregnant - the diverter valve
>does serve the function of venting excess pressure to atmosphere. the
>air pump serves the purpose of inducing air into the system to eliminate
>unburned fuel. overun is the one scenario where it is possible for a
>volume of unburned fuel to be sent out the tailpipe. ted
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Yes, I guess we are. I suppose it's one of those things. Everybodys
interpretation of something is a little different. In this case I was
*assuming* that the backfire that these listers were talking about was
similar to the one I had on my truck, since disconnecting the air pump
relieved the symptoms. The valve, (where I have read it's function) should
vent to atmosphere on immediate deceleration for about two to three
seconds, then redirect the pump air to the rail. The two to three seconds
of venting upon immediate deceleration is what prevents the loud backfire
common when this valve fails, because, as you correctly stated there is a
very rich mixture when you snap the throttle closed, and if you were
injecting air into the exhaust manifold at this same time, with this
excess, then it continues to burn, right out the tailpipe with startling
results!!
Barry Schwartz (San Diego) bschwart@pacbell.net
72 FI, V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (long term project)
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