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| Vacuum pump problem/question [message #203514] |
Wed, 03 April 2013 11:30  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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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.
My vacuum pump, installed by my beloved PO is not the typical JC4. I don't know what it is. However, it has an input (suction) and an output (exhaust). The suction line from the pump went to the booster and did indeed suck. The manifold vacuum was hooked to the exhaust port of the pump through a check valve. I see no other ports on the vacuum pump. The pump has to have a supply source but somehow I'm thinking it should not end up pushing air into the manifold.
So what is going on here? Is the check valve on the manifold vacuum line bad or backward? It's got to exhaust somewhere. What is the normal hook up for the manifold vacuum and a single booster port?
On my new sensitized booster, I had an extra vacuum port installed so I can hook manifold vacuum to one port and the pump vacuum line to the other (with check valves). No problem there but I guess I need a screen or something to keep critters from nesting in the pump.
And what vehicles have the JC4 vacuum pumps? And where are they typically located?
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
[Updated on: Wed, 03 April 2013 11:59] Report message to a moderator |
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| Re: [GMCnet] Vacuum pump problem/question [message #203522 is a reply to message #203514] |
Wed, 03 April 2013 12:14  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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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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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| 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: -74
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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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| Re: [GMCnet] Vacuum pump problem/question [message #203535 is a reply to message #203522] |
Wed, 03 April 2013 13:46 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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That is the same pump I am using and it is plumbed the same way as you have it.
Ken B.
| Ken Henderson wrote on Wed, 03 April 2013 12:14 |
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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Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Vacuum pump problem/question [message #203540 is a reply to message #203531] |
Wed, 03 April 2013 14:06 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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No need for resivour if you have a pump
Just adds more places to leak
Gene
FREE WIFI @ Mickey D
On Apr 3, 2013, at 11:12 AM, Johnny Bridges <jhbridges@ymail.com> wrote:
> 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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| Re: [GMCnet] Vacuum pump problem/question [message #203542 is a reply to message #203535] |
Wed, 03 April 2013 14:23 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
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| Ken Burton wrote on Wed, 03 April 2013 13:46 |
That is the same pump I am using and it is plumbed the same way as you have it.
Ken B. ...
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Ken, do you mean the same way I have it NOW? That is, into two ports in the booster? Do you have anything like a screen over the exhaust?
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Vacuum pump problem/question [message #203547 is a reply to message #203542] |
Wed, 03 April 2013 15:23 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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the JC4 is made to mount that way
see here,by Jerry Work
http://www.gmcmhphotos.com/photos/vacuum-booster-pump-auxiliary-gmc-jc4/p36461-work-s-pump-mount-small.html
and here
http://www.gmcmhphotos.com/photos/vacuum-booster-pump-auxiliary-gmc-jc4/p23838-vacuum-pump.html
when you get tired of the old pump
gene
On Wed, Apr 3, 2013 at 12:23 PM, Kerry Pinkerton <Pinkertonk@mchsi.com>wrote:
>
>
> Ken Burton wrote on Wed, 03 April 2013 13:46
> > That is the same pump I am using and it is plumbed the same way as you
> have it.
> > Ken B. ...
>
>
> Ken, do you mean the same way I have it NOW? That is, into two ports in
> the booster? Do you have anything like a screen over the exhaust?
> --
> Kerry Pinkerton
>
> North Alabama, near Huntsville,
>
> 77 Eleganza II, "The Lady", 403CI, also a 76 Eleganza being re-bodied as
> an Art Deco car hauler
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--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Vacuum pump problem/question [message #203583 is a reply to message #203542] |
Wed, 03 April 2013 22:02 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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No, I meant that I only have one port in the booster and the vacuum pump is inline between the intake manifold and booster. That is the way GM did it when they used those pumps on small displacement engines that had low vacuum situations.
I have had it installed for about 8 years and it was a used junkyard pump when I got it. The amount of air it exhausts into the manifold is no different that the amount of air coming from the booster without the pump installed. The air source is coming from the booster not the pump.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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