At 03:24 PM 4/26/98 -0700, Bob Sykes wrote:
>I'm not sure if your car has the gulp (diverter) valve. Early '79s
>did not have it (like '78s). ISTR late '79s did have it.
My car is an early 79 (built October 78 according to the sticker on the
door jam). It has the single tube from the air pump to the exhaust
manifold. (As in the Vicky Brit catalogue page 92, lower left corner.)
Only has a check valve AFAIK.
> This
>would be the first culprit to check. Your backfire is due to high
>back-pressure in the exhaust manifold generated by the air pump,
>coupled with lots of intake vacuum (throttle closed, high rpm).
>This causes unburnt fuel to be sucked back into the motor.
>The gulp valve was fitted to most NA spec Spits with air pump
>to alleviate this condition.
>
>Try temporarily disconnecting the air pump at the check valve.
>Plug the check valve with a bit of old rag to stop the diaphram
>from rattling when the engine is running. This should cause
>the backfiring to cease.
I'll try that tomorrow, its raining today. :( If the rag eliminates the
backfire, should I install the gulp (diverter) valve shown in the upper
right picture of the same VB page, #3?
Thanks, Bob.
Atwell Haines
'79 Spitfire FM96062 UO
Succasunna, NJ USA
OPTIMIST: A Spitfire owner who expects his car to run FLAWLESSLY and
fastens his seat belts BEFORE starting his car.
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