Home » Public Forums » GMCnet » Switching Reserve Tank (A couple small questions after a trip. )
| Switching Reserve Tank [message #298220] |
Mon, 28 March 2016 10:10  |
Dan
Messages: 99
Registered: August 2014
Location: Allentown, NJ
Karma: 0
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Hello,
About 10 miles from home I noticed a slight hesitation going up hills. My gas gauge which works intermittently showed a little less then a quarter tank, so I pulled over a put some fuel in and did not feel the hesitation again. I always leave my switch on main tank, honestly have no idea if the tank selector even works. This makes me think that somewhere along the line my Main tank became my front tank, which is backwards. Is this something even worth messing with, as everything seems to work with gas in the tanks?
When I felt the hesitation I also heard two large bangs a seconds apart. It sounded like something firmly hitting glass or the plywood floor, it did not sound mechanical and I did not feel it through the drive train. Now I am chalking this up to unseen road debris since it did not happen again, but though I'd mention it in case I am missing something.
Dan DeLuca
1978 Eleganza II (http://imgur.com/gallery/YFHhK)
Parked at Evil Monkey Farm in
Allentown, New Jersey
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| Re: [GMCnet] Switching Reserve Tank [message #298225 is a reply to message #298220] |
Mon, 28 March 2016 10:42  |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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Read here
http://gmcmotorhome.info/tank.html
On Monday, March 28, 2016, Daniel DeLuca wrote:
> Hello,
>
> About 10 miles from home I noticed a slight hesitation going up hills. My
> gas gauge which works intermittently showed a little less then a quarter
> tank, so I pulled over a put some fuel in and did not feel the hesitation
> again. I always leave my switch on main tank, honestly have no idea if the
> tank selector even works. This makes me think that somewhere along the
> line my Main tank became my front tank, which is backwards. Is this
> something
> even worth messing with, as everything seems to work with gas in the tanks?
>
> When I felt the hesitation I also heard two large bangs a seconds apart.
> It sounded like something firmly hitting glass or the plywood floor, it did
> not sound mechanical and I did not feel it through the drive train. Now
> I am chalking this up to unseen road debris since it did not happen again,
> but though I'd mention it in case I am missing something.
> --
> Dan DeLuca
> 1978 Eleganza II (http://imgur.com/gallery/YFHhK)
> Parked at Evil Monkey Farm in
> Allentown, New Jersey
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
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: Switching Reserve Tank [message #298230 is a reply to message #298220] |
Mon, 28 March 2016 12:10 |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Dan,
When I replaced my tank selector valve, I reversed the tanks on purpose. If you look at the tank plumbing diagrams here: http://gmcmotorhome.info/tank.html you will see that due to the location of the filler lines on the tanks, going down hill (and braking to boot!) can quickly drain your rear (main) tank. My new valve uses a motor in to do the switching so I needed to add a relay to power it anyway. Changing back is just a matter of moving 2 wires in the relay.
I have fuel injection so I notice when the pump is not getting fuel right away, as opposed to a carb which has a bit of reserve in the bowl.
As a rule, once I hit 1/2 tank level, I'm looking to fill up. My butt is numb and bladder is full so I need a break too!
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: [GMCnet] Switching Reserve Tank [message #298240 is a reply to message #298230] |
Mon, 28 March 2016 16:05 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Your old selector switch need to be replaced as the Ethanol has eaten the
rubber up and is hanging up.
Also you better call me so I can tell you what all you'll need to do as
this is only the surface of problems ....
On Mon, Mar 28, 2016 at 10:10 AM, Bruce Hislop wrote:
> Dan,
> When I replaced my tank selector valve, I reversed the tanks on purpose.
> If you look at the tank plumbing diagrams here:
> http://gmcmotorhome.info/tank.html you will see that due to the location
> of the filler lines on the tanks, going down hill (and braking to boot!) can
> quickly drain your rear (main) tank. My new valve uses a motor in to do
> the switching so I needed to add a relay to power it anyway. Changing back
> is
> just a matter of moving 2 wires in the relay.
>
> I have fuel injection so I notice when the pump is not getting fuel right
> away, as opposed to a carb which has a bit of reserve in the bowl.
>
> As a rule, once I hit 1/2 tank level, I'm looking to fill up. My butt is
> numb and bladder is full so I need a break too!
>
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
> Hubler 1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Switching Reserve Tank [message #298247 is a reply to message #298240] |
Mon, 28 March 2016 17:42 |
Dan
Messages: 99
Registered: August 2014
Location: Allentown, NJ
Karma: 0
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Member |
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Thanks Jim, I probably will be making a order soon as I did the entire fuel system accept for the selector valve, the vapor separator and the canister. Now that I think about it those bangs were almost certainly lean backfires. Probably should sort the fuel guage while I'm at it.
Dan DeLuca
1978 Eleganza II (http://imgur.com/gallery/YFHhK)
Parked at Evil Monkey Farm in
Allentown, New Jersey
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| Re: Switching Reserve Tank [message #298250 is a reply to message #298220] |
Mon, 28 March 2016 18:13 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The standard gas tank plumbing will allow gas flow to the rear tank from the front when going up hill. When going down hill some, but much less, gas will transfer from the rear to the front. This is because the filler pipes for both tanks for are mounted nearer the rear of both tanks. The transfer of fuel between tanks occurs through that filler pipe. I would rather not run out of fuel going up hill, so I would leave it plumbed as designed by GM.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Switching Reserve Tank [message #298255 is a reply to message #298250] |
Mon, 28 March 2016 18:55 |
Scott Nutter
Messages: 782
Registered: January 2015
Location: Houston/San Diego
Karma: 4
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Senior Member |
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Ken,
Very good point....
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI
Houston, Texas
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| Re: [GMCnet] Switching Reserve Tank [message #298260 is a reply to message #298259] |
Mon, 28 March 2016 19:41 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Now you know why I recommend starting each trip with full tanks, then drive
4 hours, then refill the tanks and continue trip. No one should sit in one
place more than 4 hours anyway. You will never have low fuel problems if
you do as I suggest.
Jim Hupy
Salem, Or
78 GMC ROYALE 403
On Mar 28, 2016 5:32 PM, "Bruce Hislop" wrote:
> Ken,
> You had me scratching my head, so I just went out to the shop and looked.
> My 1977 model year Palm Beach (built in October '76) has the filler for both
> tanks at the front as per Gene's diagram. So it will work as per the
> diagrams. Very little transfer to the back going uphill and maximum
> transfer to
> the front going downhill. I had this happen with about within the first
> year of ownership. 1/4 tank going down a short hill, braking and turning to
> the right into a grocery store parking lot. I remember being thankful for
> the newly installed vacuum pump on the power brakes.
>
> Did they change the filler location?
> --
> Bruce Hislop
> ON Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
> Hubler 1 ton front end
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> My Staff says I never listen to them, or something like that
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Switching Reserve Tank [message #298270 is a reply to message #298259] |
Tue, 29 March 2016 01:29 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Well, I now have me scratching my head also.
I frequently run mine until it runs out of gas on the main and then switch to the reserve (front) tank while I continue on my way looking for a gas station in the next 50 miles.
I'll have to go look at mine again.
I admit that there are not a lot of long hill climbs around here.
Sorry,
Ken
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Switching Reserve Tank [message #298289 is a reply to message #298270] |
Tue, 29 March 2016 12:12 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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[quote title=Ken Burton wrote on Mon, 28 March 2016 23:29]Well, I now have me scratching my head also.
I frequently run mine until it runs out of gas on the main and then switch to the reserve (front) tank while I continue on my way looking for a gas station in the next 50 miles.
I'll have to go look at mine again.
I admit that there are not a lot of long hill climbs around here.
Sorry,
Ken
I have done it that way but in the open desert it gets hairy when the low fuel light is on with both tanks. What I need to do when the tanks get lower than they should be is switch to the main tank on an uphill climb and then switch to the auxiliary going down till I find a gas station.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Switching Reserve Tank [message #298290 is a reply to message #298220] |
Tue, 29 March 2016 12:13 |
tgeiger
Messages: 518
Registered: February 2006
Location: kansas city
Karma: -1
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Senior Member |
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Low fuel light, now I'll have to see why mine isn't working. I've run out of gas and no light has come on for me.
I too wonder if my tank selector is working anymore. Doesn't switching to that allow you to read the last 1/4 or so of your second tank?? May have that wrong but I never knew the value of switching that with the 4 hour rule.
I go by the 4 hour, or less rule too. Figure it would be better safe than sorry on the side of the road.
Tom Geiger
76 Eleganza II
KCMO
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| Re: Switching Reserve Tank [message #298309 is a reply to message #298290] |
Tue, 29 March 2016 18:07 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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tgeiger wrote on Tue, 29 March 2016 10:13Low fuel light, now I'll have to see why mine isn't working. I've run out of gas and no light has come on for me.
I too wonder if my tank selector is working anymore. Doesn't switching to that allow you to read the last 1/4 or so of your second tank?? May have that wrong but I never knew the value of switching that with the 4 hour rule.
I go by the 4 hour, or less rule too. Figure it would be better safe than sorry on the side of the road.
If you have run out of gas and switching to the other tank still leaves you with not enough fuel to start the engine my guess is the selector valve is either not switching tanks or it has a bad seal in the valve alowing it to suck air from the empty tank which would prevent it from pumping gas out of the selected tank.So you may have two problems. For me two electric pumps and no selector valve or manual pump works better in hot weather.
Roy Keen
Minden,NV
76 X Glenbrook
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