Runs better with vacuum line unhooked?

[Blue71]

The '68 all stock seems to run much better for some reason with the vacuum wiper hose off of vacuum porton on the manifold behind the carb. When wiper vacuum line is hooked up...you can rev it up with a quick sharp thrust of the throttle arm and it has a slight hesitation. You can unhook the vacuum line from the port (motor idles higher when unhooked) and leave it open to suck air and it will rev instantly when the throttle is moved sharply. Much more responsive with it drawing outside air. Usually on all the other Broncos....I can unhook a vacuum line and it runs like crap till I hook it ack up? Any suggestions? Thanks Much,

Blue71

 

[70TEXEB]

Your vacum advance may be wore out. First remove dist cap so you can see the advance mechanism then put a hose on it or disconnect at carb and suck on line and hold for a few seconds if it releases before you let off suction the diaphram is probably bad. Or if it never engages when you suck.

oops, sorry you were talking about the vacum line in back. ;D

 

[dpmerrill]

Have you double checked your idle adjustment? You may just be running too rich.

I would also look at your accelerator pump linkeage. It could be pushing too much fuel when you hit the gas. You may also try disconnecting the accelerator pump altogether (with your vacuum lines hooked up), and see how that changes things.

Hopefully it's something simple like timing or carb adjustment. If the problem is in your secondaries, it could be time to try rebuilding the carb.

 

[Mr Joe]

I agree, sounds like the accelerator pump is setup too rich....

 

[wildbill]

%) %) %) Running a little rich but dont run with the vacuum line unhooked as it will burn the valves good luck. %) %) %) Bill %)

 

[kwspony]

you could also have leaks in your wiper motors. you may have to re-tune the carb with the motors hooked up and then re-tune when not hooked up. Or just swap over to electric motors.

 

[YellowBronc]

I would check timing first. Do you have a vacuum gauge? hook it up to manifold vacuum and see what you have. It just sounds to me as a timing issue before I would blame it on the carb.