| Re: [GMCnet] Vacuum pump problem/question [message #203531 is a reply to message #203522] |
Wed, 03 April 2013 13:12   |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma:
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Senior Member |
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I got one of those to install. It has an internal check valve, I'm gonna simply plumb the suction line into the (new) vacuum reservoir, and let the pump purge to ambient air through a second check valve and a screen. The manifold line comes in through a check valve also. This way, an MAP increase won't let the reservoir pressure rise. I'll have proper (low) pressure for the heater controls and the brakes. A piece of capped 4 inch PVC a couple feet long will provide several stops before the pump comes on. I haven't figured a way to put a 'run' light on it since the switch is internal. I may just put a pressure switch on the reservoir with an alarm light on the dash. If reservoir pressure gets within 8 - 10 inches of ambient, I wanna know it. How it got there can be determined after I (carefully) get the coach out of traffic and stopped.
--johnny
________________________________
From: Ken Henderson <hend4800@bellsouth.net>
To: gmclist <gmclist@temp.gmcnet.org>
Sent: Wednesday, April 3, 2013 1:14 PM
Subject: Re: [GMCnet] Vacuum pump problem/question
Kerry,
Does your vacuum pump look like this one:
http://www.gmcmhphotos.com/photos/vacuum-pump-repair/p39177-vacuum-pump-fix.html
or
http://goo.gl/CtyB5
If so, it's supposed to go in series in the hose from the intake manifold
to the vacuum booster. So it will indeed blow back into the manifold, as
long as there's air to be exhausted from the booster -- just as the engine
should be doing when running.
Fact is, with your new booster, if still using the illustrated pump, you
shouldn't use the second booster port.
Ken H.
On Wed, Apr 3, 2013 at 12:30 PM, Kerry Pinkerton wrote:
>
>
> Paul and Nancy Doane visited last night and he drove my coach. I started
> asking some questions about vacuum and he noticed that while my coach ran
> great, the vacuum guage read a bit higher than his did. This morning
> before they left we did some poking and Paul noticed that when the vacuum
> pump came on, it blew back through the manifold and up through the carb.
> We pulled the booster vacuum line and sure enough when you press the brake
> pedal to trigger the pump, it blows back through the manifold vacuum line.
> ...
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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