gmbchef

A few weeks ago I was having leaning condition under high boost. Everything was working as they should, and found that the wastegate actuation stud was stripped, causing the diaphragm to lift, letting the boost spike. Fixed that, same problem. So...after lots of urq list archiving and remembering some of the Bosch book topics, I remembered that the WUP on this car was set up for cold running as well as boost enrichment, but the hose set up made no sense to me. I have tinkered with that before, but never quite figured it out. This time, I took an old WUP (CPR) apart, and applied pressure to both nipples then vacuum to both nipples. What I found was that the two nipples are placed in such a way that the diaphragm moves the same direction under boost as well as vaccum, the large one being the boost enrichment. What didn't make sense is the on-off switch below #5 cylinder plug, with the two nipples on it. It has one hose from the manifold going to it, and one hose that is teed off to go to both the large and small nipples on the WCUPR. When the motor gets warm, the switch closes, and therefore no vacuum or pressure goes to the CWPUR. This is as per the underhood and IST docs. So....I by passed the switch all together...guess what....enrichment under high boost! But, now enrichment under decel too. When I re-install the vacuum hose from the manifold to the switch and the switch to the small nipple, that will take care of that. But, it does sound cool with that rolling burble under in-gear decel! I'm sure that this has been written up somewhere, but I couldn't find it.

HTH

Gary

Jretal

great info, thanks Gary! I'm assuming that w/o the WOT enrichment when under heavy boost the car would studder when trying to accel? Need to check that out in addition to the WG diaphram on our '83 since we're getting cut outs above 5k rpm at WOT, but runs to redline when doing part throttle.