Vacuum Leak
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Senior User
Joined: Dec 2004
Posts: 320
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From: Dallas, Texas
Vacuum Leak
I've finally decided that my 81 has a vacuum leak somewhere. When I cover the air intake at the carburator, the idle smooths out. I can't find a leak anywhere, so I suppose the next step is to unplug all non-essentials so that the leak can be found. My question for ya'll is if some of the colored thin lines that plug into the carburator are unnecessary and can be stopped up on one end or the other to elliminate certain lines. Really, any help I can get to find this leak would be of help, because its idling VERY rough right now.
thanks in advance,
Matt
thanks in advance,
Matt
Senior User
Joined: Jul 2005
Posts: 258
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From: Black Hills South Dakota
I'd go more with it running too lean. How's the plugs look?
Hard to believe, but every hose on there has a purpose. Yank one or more, maybe it'll run different, maybe not, since it may have to be cold or hot or under load for it to matter. If you're bound to try it, start the rig after or while you make just a single change or two so you know if you yank something important. Take pictures, make a sketch or somehow tag stuff so you can replace it if need be.
You could buy a hand-vacuum pump so you can test the lines with the motor shut off. See what bleeds down or makes leaking sounds.
-Ed
-Ed
Hard to believe, but every hose on there has a purpose. Yank one or more, maybe it'll run different, maybe not, since it may have to be cold or hot or under load for it to matter. If you're bound to try it, start the rig after or while you make just a single change or two so you know if you yank something important. Take pictures, make a sketch or somehow tag stuff so you can replace it if need be.
You could buy a hand-vacuum pump so you can test the lines with the motor shut off. See what bleeds down or makes leaking sounds.
-Ed
-Ed
Senior User
Joined: Jul 2005
Posts: 258
Likes: 0
From: Black Hills South Dakota
I'd go more with it running too lean if reducing the airflow smooths it. How's the plugs look? Bone white and blasted, it's too lean.
Hard to believe, but every hose on there has a purpose. An awful lot of purposes! Count on one or two functions per hose. Yank one or more, maybe it'll run different, maybe not, since it may have to be cold or hot or under load for it to matter. If you're bound to try it, start the rig after or while you make just a single change or two so you know if you yank something important. Take pictures, make a sketch or somehow tag stuff so you can replace it if need be.
You could buy a hand-vacuum pump so you can test the lines with the motor shut off. See what bleeds down or makes leaking sounds.
-Ed
Hard to believe, but every hose on there has a purpose. An awful lot of purposes! Count on one or two functions per hose. Yank one or more, maybe it'll run different, maybe not, since it may have to be cold or hot or under load for it to matter. If you're bound to try it, start the rig after or while you make just a single change or two so you know if you yank something important. Take pictures, make a sketch or somehow tag stuff so you can replace it if need be.
You could buy a hand-vacuum pump so you can test the lines with the motor shut off. See what bleeds down or makes leaking sounds.
-Ed
Posting Guru
Joined: Apr 2005
Posts: 2,246
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From: Hawkeye Country
go over every single vacume line, im sure you can eliminate alot of junk off of the side of your carb, my 82 has 3 lines out of the vacume tree the big one for the brake booster, a smaller one that goes to the tranny, and the one for the vacume advance. other then that the rest are caped off. also check the intake/exhaust manifold gasket, a quick test is to spray the area with soapy water and check for bubbles
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Senior User
Joined: Dec 2004
Posts: 320
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From: Dallas, Texas
If it could be the intake manifold seal, then maybe I know why. With my engine came a box of new gaskets. It came with a shiny metal plated gasket for the manifold, that I put on, but it also came with another gasket that looks like it goes on the intake. I didn't put this one on because I thought all I would need is the shiny gasket, but maybe this is the reason for my problems. any thoughts?
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Joined: Mar 2003
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From: Northeast Wisconsin
Idle the engine. Listen for a noticable change in rpm as you spray all vacuum connections, the intake manifold gasket, the throttle body gasket, and any other vacuum-using device with an aerosol spray can of cheap carb cleaner. If you have a vacuum leak, you'll notice a definite change in rpm when the spray is sucked into the hole and gets vaporized. Don't use WD-40, as it doesn't vaporize fast enough to give you a noticeable rpm change on a small leak.
