Sounds like pump cavitation to me! Dunno how you would check it though.

John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com

On 7/15/2010 4:19 PM, Sam Payne wrote:
> The injectors were cleaned recently, and have only seen about 3,000 miles since. Also, the fuel
> pressure with the pump running tests dead on, and the residual pressure stays up for long
> enough.
>      I haven't tried disconnecting the O2 sensor, and will. Thanks for the suggestion.
>       But why the bubbles?
>
>          thanks, Sam
>
>