The dual action pump is actuall two diaphagm pumps in one housing. the top pump pumps fuel to the carburestor and the lower pump only supplies vaccum to the vacuum wiper circuit. Therefore when you open the throttle which causes the vacuum to drop in the manifold, because the induction system is essentually open to atmosphere, a vacuum source is still avalable to the wipers.
DG
Last edited by Denny Graham; 09/02/2009 2:12 AM.
