greenteagod
+1y
So to preface this topic, you might see one of my others in the repair section regarding emissions testing. I've failed three times now due to high CO and HC.
I had some vacuum stuff still hooked up, namely that whatever it is magic box on the drivers side and the lines that went to the thermo switch. On the side of the thermo switch there's a little port that seems to have a cotton filter in it, I found it was the source of a big vacuum leak, which it seems to be intended to be under certain conditions. It was causing a leak enough all the time though that at idle (800 RPM) I'd put my finger over it and it would drop down in to the 500s. So I started tracing vacuum lines back and eventually got everything capped off and that switch removed from the system. Got the idle set at 750 rpm, checked for leaks with some carb spray and all was good.
Then I go to drive it. If I got on it at all it would start pinging something fierce. My temp gauge would shoot up and then once things got hot it was all over. Not enough power to keep it at 50, pull over let it cool off and try again while praying it's all down hill.
The only other vacuum thing I could think of was the vacuum advance. I have it hooked straight from the weber right to the distributor port. I yanked it, capped the port going to the carb and like magic I'm doing 80 down the highway with the AC on and still have throttle to go.
So here's my inquiry. Is it possible that with capping off everything else that the vacuum is so strong it's causing the distributor to advance too much? I get that I'd have a bit more power with the advance working properly but having it hooked up makes the truck undriveable. I'm not 100% familiar with the way the vacuum advance works so maybe the diaphragm is worn and causing it to advance too much, not sure if there'd be a limit in it as far as how far it would advance things.
That's really my only guess on it as thinking other things out end up coming to a dead end in my line of logic.
I have another free go on the emissions testing so I'm hoping this has sorted it out. I'd like to have the advance hooked up, but not if it's advancing things too much. And with that I'll end this chapter.