Home » Public Forums » GMCnet » connected fuel tanks
| connected fuel tanks [message #169438] |
Sun, 13 May 2012 15:01  |
jayrabe
Messages: 509
Registered: June 2009
Location: Portland, OR
Karma: 0
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Senior Member |
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I know I've seen a mention of connecting the fuel tanks together at the drain IIRC and eliminating the selector valve. Seemed like a good idea, with lots of benefits. Neither Google nor searching on birdfeeder came up with anything less than 800,000 hits to my search terms...
So, first, can someone give me a link or some info on how to go about it?
Second, is there any downside to doing this?
Thanks,
Jay Rabe
76 PB
Portland, OR
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| Re: connected fuel tanks [message #169440 is a reply to message #169438] |
Sun, 13 May 2012 15:16  |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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| jayrabe wrote on Sun, 13 May 2012 16:01 |
I know I've seen a mention of connecting the fuel tanks together at the drain IIRC and eliminating the selector valve. Seemed like a good idea, with lots of benefits. Neither Google nor searching on birdfeeder came up with anything less than 800,000 hits to my search terms...
So, first, can someone give me a link or some info on how to go about it?
Second, is there any downside to doing this?
Thanks,
Jay Rabe
76 PB
Portland, OR
|
I would think it would be hard to protect the connecting line from road debree. I have seen many tankd with dents, scrapes, and gouges. The tanks are directly connected by the fill line and fuel migrates to the rear tank except for 7 gal that is accessable from a dash switch. Seems a better idear to me.
C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] connected fuel tanks [message #169442 is a reply to message #169440] |
Sun, 13 May 2012 15:36 |
Gary Worobec
Messages: 867
Registered: May 2005
Karma: -1
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Senior Member |
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Hi,
Jim Bounds is an advocate of doing this. In fact we discussed it at the Casa
de Fruta rally. Jim has some interesting parts for this namely some 90
degree compression fittings with threads that will allow the elbows to screw
in very close to the tank. Then he recommends steel line in a bit of an "S"
shape to connect the tanks to allow for any movement. He uses compression
fittings. This is an all steel line and fitting set up I believe. I
suggested SS over teflon hose but he countered by saying that it would be
difficult to support the hose from drooping. I agreed with him after our
discussion. For folks with EFI I think this would be a good mod as the tanks
would remain the same level all the time. As it is the return fuel for the
EFI sometimes give me false readings. This is a mod I am going to give some
real consideration to.
Be good if Jim could chime in to give details. I don;t want to mis-state
what we discussed.
Thanks
Gary and Joanne Worobec
1973 GMC Glacier
Anza, CA
----- Original Message -----
From: "Charles Boyd" <covered-wagon@comcast.net>
To: <gmclist@temp.gmcnet.org>
Sent: Sunday, May 13, 2012 1:16 PM
Subject: Re: [GMCnet] connected fuel tanks
>
>
> jayrabe wrote on Sun, 13 May 2012 16:01
>> I know I've seen a mention of connecting the fuel tanks together at the
>> drain IIRC and eliminating the selector valve. Seemed like a good idea,
>> with lots of benefits. Neither Google nor searching on birdfeeder came up
>> with anything less than 800,000 hits to my search terms...
>>
>> So, first, can someone give me a link or some info on how to go about it?
>>
>> Second, is there any downside to doing this?
>>
>> Thanks,
>>
>> Jay Rabe
>> 76 PB
>> Portland, OR
>
>
>
>
>
>
>
> I would think it would be hard to protect the connecting line from road
> debree. I have seen many tankd with dents, scrapes, and gouges. The tanks
> are directly connected by the fill line and fuel migrates to the rear tank
> except for 7 gal that is accessable from a dash switch. Seems a better
> idear to me.
> --
> C. Boyd
> 76 Crestmont by Midas
> East Tennessee
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] connected fuel tanks [message #169445 is a reply to message #169442] |
Sun, 13 May 2012 16:06 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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I am going to do this to my 2 GMCs
One of the lens has this. But does not talk about it much
Gene
FREE WIFI @ Mickey D
On May 13, 2012, at 1:36 PM, "Gary Worobec" <gtw5@earthlink.net> wrote:
> Hi,
> Jim Bounds is an advocate of doing this. In fact we discussed it at the Casa
> de Fruta rally. Jim has some interesting parts for this namely some 90
> degree compression fittings with threads that will allow the elbows to screw
> in very close to the tank. Then he recommends steel line in a bit of an "S"
> shape to connect the tanks to allow for any movement. He uses compression
> fittings. This is an all steel line and fitting set up I believe. I
> suggested SS over teflon hose but he countered by saying that it would be
> difficult to support the hose from drooping. I agreed with him after our
> discussion. For folks with EFI I think this would be a good mod as the tanks
> would remain the same level all the time. As it is the return fuel for the
> EFI sometimes give me false readings. This is a mod I am going to give some
> real consideration to.
>
> Be good if Jim could chime in to give details. I don;t want to mis-state
> what we discussed.
>
> Thanks
>
> Gary and Joanne Worobec
> 1973 GMC Glacier
> Anza, CA
>
>
>
> ----- Original Message -----
> From: "Charles Boyd" <covered-wagon@comcast.net>
> To: <gmclist@temp.gmcnet.org>
> Sent: Sunday, May 13, 2012 1:16 PM
> Subject: Re: [GMCnet] connected fuel tanks
>
>
>>
>>
>> jayrabe wrote on Sun, 13 May 2012 16:01
>>> I know I've seen a mention of connecting the fuel tanks together at the
>>> drain IIRC and eliminating the selector valve. Seemed like a good idea,
>>> with lots of benefits. Neither Google nor searching on birdfeeder came up
>>> with anything less than 800,000 hits to my search terms...
>>>
>>> So, first, can someone give me a link or some info on how to go about it?
>>>
>>> Second, is there any downside to doing this?
>>>
>>> Thanks,
>>>
>>> Jay Rabe
>>> 76 PB
>>> Portland, OR
>>
>>
>>
>>
>>
>>
>>
>> I would think it would be hard to protect the connecting line from road
>> debree. I have seen many tankd with dents, scrapes, and gouges. The tanks
>> are directly connected by the fill line and fuel migrates to the rear tank
>> except for 7 gal that is accessable from a dash switch. Seems a better
>> idear to me.
>> --
>> C. Boyd
>> 76 Crestmont by Midas
>> East Tennessee
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
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| Re: connected fuel tanks [message #169448 is a reply to message #169438] |
Sun, 13 May 2012 16:29 |
shawnee
Messages: 422
Registered: February 2004
Location: NC
Karma: 0
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Senior Member |
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| jayrabe wrote on Sun, 13 May 2012 16:01 |
I know I've seen a mention of connecting the fuel tanks together at the drain IIRC and eliminating the selector valve. Seemed like a good idea, with lots of benefits. Neither Google nor searching on birdfeeder came up with anything less than 800,000 hits to my search terms...
So, first, can someone give me a link or some info on how to go about it?
Second, is there any downside to doing this?
Thanks,
Jay Rabe
76 PB
Portland, OR
|
Jay,
I gave up on the selector valve and installed Carter 4070 fuel pumps for each tank. I used two relays to send power to each fuel pumps through a selector switch that turns on each pump by activating the relay using the ground wire which goes through my oil pressure switch. I also use a large filter before each fuel pump to make sure I don't get the black sludge from each tank. Works for me and gives me an installed spare pump.
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
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| Re: [GMCnet] connected fuel tanks [message #169449 is a reply to message #169442] |
Sun, 13 May 2012 16:48 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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I won't deny that there are some things to be said for combining the tanks
-- elimination of the selector valve being the only one I can think of at
the moment. But I personally wouldn't want to do it; I need to have a
reserve tank for those times when I mis-read, can't rely on, or ignore the
main tank gauge. And I HAVE eliminated the selector valve -- by installing
separate electric pumps for the two tanks. That gives me almost complete
redundancy. And the fact that the Aux pump is used only when I've emptied
the Main tank means it doesn't get much use.
While I had that pump arrangement long before installing EFI, that update
makes me even more fond of it. Since my return line goes into the drain
fitting on the Aux tank, that tank ALWAYS has the 6 gallon reserve below
the fill tube. There's never any doubt about where my fuel is, with the
possible exception of during a long up-hill climb. In that case, I'd still
prefer to have SOME fuel trapped in the forward tank instead of all of it
flowing to the rear of the rear tank -- it's doubtful that all 6 gallons
will be unreachable on any grade the GMC will climb (no, I haven't done the
trigonometry).
It was easy to provide what I consider adequate protection for the return
line to the forward tank since there's a cross member just ahead of it, to
which I bolted a hefty steel channel skid guard for the line. If I were
going to connect all the way to the rear tank, I'd try to run a guard all
the way from that cross member to the one behind the rear tank.
JMHO -- YDWSU (You Do What Suits yoU) :-)
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
> jayrabe wrote on Sun, 13 May 2012 16:01
> >> I know I've seen a mention of connecting the fuel tanks together at the
> >> drain IIRC and eliminating the selector valve. Seemed like a good idea,
> >> with lots of benefits. Neither Google nor searching on birdfeeder came
> up
> >> with anything less than 800,000 hits to my search terms...
> >>
> >> So, first, can someone give me a link or some info on how to go about
> it?
> >>
> >> Second, is there any downside to doing this?
>
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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] connected fuel tanks [message #169452 is a reply to message #169445] |
Sun, 13 May 2012 17:41 |
Marc Hogenboom[2]
Messages: 70
Registered: March 2011
Karma: 0
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Member |
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Both my tanks are connected as well, but I put in a fuel pump to move the
fuel from the forward tank into the rear.
I also put the fuel senders in series and connected them to a 90 Ohm fuel
gauge , so I always have a reasonably accurate reading.
The forward fuel sender has to be isolated from ground to make this work. I
did that by cutting the puck up tube above the ground, connecting the tube
with fuel hose, and soldering a ground wire on the lower part of the tube.
I'll try and post a picture tomorrow, as my diner guests are now about to
arrive.
So far the system seems to work well.
Marc Hogenboom
'73 Painted Desert Diesel
Madrid NM
-----Oorspronkelijk bericht-----
From: mr.erfisher@gmail.com
Sent: Sunday, May 13, 2012 3:06 PM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] connected fuel tanks
I am going to do this to my 2 GMCs
One of the lens has this. But does not talk about it much
Gene
FREE WIFI @ Mickey D
On May 13, 2012, at 1:36 PM, "Gary Worobec" <gtw5@earthlink.net> wrote:
> Hi,
> Jim Bounds is an advocate of doing this. In fact we discussed it at the
> Casa
> de Fruta rally. Jim has some interesting parts for this namely some 90
> degree compression fittings with threads that will allow the elbows to
> screw
> in very close to the tank. Then he recommends steel line in a bit of an
> "S"
> shape to connect the tanks to allow for any movement. He uses compression
> fittings. This is an all steel line and fitting set up I believe. I
> suggested SS over teflon hose but he countered by saying that it would be
> difficult to support the hose from drooping. I agreed with him after our
> discussion. For folks with EFI I think this would be a good mod as the
> tanks
> would remain the same level all the time. As it is the return fuel for the
> EFI sometimes give me false readings. This is a mod I am going to give
> some
> real consideration to.
>
> Be good if Jim could chime in to give details. I don;t want to mis-state
> what we discussed.
>
> Thanks
>
> Gary and Joanne Worobec
> 1973 GMC Glacier
> Anza, CA
>
>
>
> ----- Original Message -----
> From: "Charles Boyd" <covered-wagon@comcast.net>
> To: <gmclist@temp.gmcnet.org>
> Sent: Sunday, May 13, 2012 1:16 PM
> Subject: Re: [GMCnet] connected fuel tanks
>
>
>>
>>
>> jayrabe wrote on Sun, 13 May 2012 16:01
>>> I know I've seen a mention of connecting the fuel tanks together at the
>>> drain IIRC and eliminating the selector valve. Seemed like a good idea,
>>> with lots of benefits. Neither Google nor searching on birdfeeder came
>>> up
>>> with anything less than 800,000 hits to my search terms...
>>>
>>> So, first, can someone give me a link or some info on how to go about
>>> it?
>>>
>>> Second, is there any downside to doing this?
>>>
>>> Thanks,
>>>
>>> Jay Rabe
>>> 76 PB
>>> Portland, OR
>>
>>
>>
>>
>>
>>
>>
>> I would think it would be hard to protect the connecting line from road
>> debree. I have seen many tankd with dents, scrapes, and gouges. The
>> tanks
>> are directly connected by the fill line and fuel migrates to the rear
>> tank
>> except for 7 gal that is accessable from a dash switch. Seems a better
>> idear to me.
>> --
>> C. Boyd
>> 76 Crestmont by Midas
>> East Tennessee
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] connected fuel tanks [message #169456 is a reply to message #169448] |
Sun, 13 May 2012 17:58 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On May 13, 2012, at 3:29 PM, Gene Dotson wrote:
>
>
> jayrabe wrote on Sun, 13 May 2012 16:01
>> I know I've seen a mention of connecting the fuel tanks together at the drain IIRC and eliminating the selector valve. Seemed like a good idea, with lots of benefits. Neither Google nor searching on birdfeeder came up with anything less than 800,000 hits to my search terms...
>>
>> So, first, can someone give me a link or some info on how to go about it?
>>
>> Second, is there any downside to doing this?
>>
>> Thanks,
>>
>> Jay Rabe
>> 76 PB
>> Portland, OR
>
>
> Jay,
>
> I gave up on the selector valve and installed Carter 4070 fuel pumps for each tank. I used two relays to send power to each fuel pumps through a selector switch that turns on each pump by activating the relay using the ground wire which goes through my oil pressure switch. I also use a large filter before each fuel pump to make sure I don't get the black sludge from each tank. Works for me and gives me an installed spare pump.
> --
> Gene Dotson
> 74 Canyonlands
> www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
> _______________________________________________
Jay
The same thing can be done by using one relay and the existing Main/Aux selector switch.
A standard 5 pin relay will have one terminal marked 30. The others are 85, 86, 87, and 87a.
You would run a fused hot wire from the front to terminal 30. If you have a TBI system use the hot wire that would normally go to the TBI fuel pump.
Terminal 85 would go to ground. Terminal 86 would use the wire from the fuel selector on the dash that used to go to the fuel tank selector.
87 (normally open - on when switch is closed) go to AUX tank pump (front tank).
8a (normally closed - on when switch is off) goes to MAIN tank pump (rear tank).
If you want to use an oil pressure switch you would connect the ground wire on terminal 85 to that pressure switch.
Emery Stora
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| Re: [GMCnet] connected fuel tanks [message #169466 is a reply to message #169456] |
Sun, 13 May 2012 20:11 |
shawnee
Messages: 422
Registered: February 2004
Location: NC
Karma: 0
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Senior Member |
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| emerystora wrote on Sun, 13 May 2012 18:58 |
On May 13, 2012, at 3:29 PM, Gene Dotson wrote:
>
> I gave up on the selector valve and installed Carter 4070 fuel pumps for each tank. I used two relays to send power to each fuel pumps through a selector switch that turns on each pump by activating the relay using the ground wire which goes through my oil pressure switch. I also use a large filter before each fuel pump to make sure I don't get the black sludge from each tank. Works for me and gives me an installed spare pump.
> --
> Gene Dotson
> 74 Canyonlands
> www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
> _______________________________________________
Jay
The same thing can be done by using one relay and the existing Main/Aux selector switch.
A standard 5 pin relay will have one terminal marked 30. The others are 85, 86, 87, and 87a.
You would run a fused hot wire from the front to terminal 30. If you have a TBI system use the hot wire that would normally go to the TBI fuel pump.
Terminal 85 would go to ground. Terminal 86 would use the wire from the fuel selector on the dash that used to go to the fuel tank selector.
87 (normally open - on when switch is closed) go to AUX tank pump (front tank).
8a (normally closed - on when switch is off) goes to MAIN tank pump (rear tank).
If you want to use an oil pressure switch you would connect the ground wire on terminal 85 to that pressure switch.
Emery Stora
Emery,
I used two relays since I wanted a separate source of power to the fuel pumps. I actually used circuit breakers instead of fuses but my concern was that if one fuse or circuit breaker went out, I could switch to the other pump on the move with a different fuse or breaker without being out of power to the pump. Somehow being on a busy Interstate road where I would have to pull off if I could, didn't interest me. I like to be able to keep going and not having to stop to wait for a circuit breaker to engage or change a fuse. Belts and suspenders you know. Relays are cheap.
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Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
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| Re: [GMCnet] connected fuel tanks [message #169554 is a reply to message #169438] |
Mon, 14 May 2012 11:30 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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I wouldn't do it, for the same reason you can't do it on low wing airplanes. Given a long hill, you stand the chance of pumping air whern there's still some gas left.
--johnny
'76 23' transmode norris
'76 palm beach
From: Jay Rabe <jayrabe@hotmail.com>
To: gmclist@temp.gmcnet.org
Sent: Sunday, May 13, 2012 4:01 PM
Subject: [GMCnet] connected fuel tanks
I know I've seen a mention of connecting the fuel tanks together at the drain IIRC and eliminating the selector valve. Seemed like a good idea, with lots of benefits. Neither Google nor searching on birdfeeder came up with anything less than 800,000 hits to my search terms...
So, first, can someone give me a link or some info on how to go about it?
Second, is there any downside to doing this?
Thanks,
Jay Rabe
76 PB
Portland, OR
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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] connected fuel tanks [message #169556 is a reply to message #169554] |
Mon, 14 May 2012 12:01 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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Given a long hill, you stand the chance of pumping air when there's still
some gas left.
>
>
less chance than -
Mickey mouse reserve
http://gmcmotorhome.info/tank.html
bad tank selector
bad senders / pickups
bad wiring
bad switches
more complexity
efi pumps to only one tank
etc
(on my second tank selector)
always fill at 1/2 tank
gene
> --johnny
> '76 23' transmode norris
> '76 palm beach
>
>
> From: Jay Rabe <jayrabe@hotmail.com>
> To: gmclist@temp.gmcnet.org
> Sent: Sunday, May 13, 2012 4:01 PM
> Subject: [GMCnet] connected fuel tanks
>
>
>
> I know I've seen a mention of connecting the fuel tanks together at the
> drain IIRC and eliminating the selector valve. Seemed like a good idea,
> with lots of benefits. Neither Google nor searching on birdfeeder came up
> with anything less than 800,000 hits to my search terms...
>
> So, first, can someone give me a link or some info on how to go about it?
>
> Second, is there any downside to doing this?
>
> Thanks,
>
> Jay Rabe
> 76 PB
> Portland, OR
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> _______________________________________________
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> Unsubscribe or Change List Options:
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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: connected fuel tanks [message #169604 is a reply to message #169438] |
Mon, 14 May 2012 18:36 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
|
Senior Member |
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Jay not quoted..
As I see it, you loose any hope of fuel management.
There is also the case for road damage to the crossover line.
And, you now have to carry twice as much fuel to be able to run the APU.
I often run (situation permitting) one of the tanks to stumble so I can switch and be certain that all that hardware is still functional. We often run one tank all the way down, then we know exactly how soon we have to fine fuel. If that happens too soon, we know that we are off on our fuel rate. Yes, I know I'm kind of paranoid, but I'm alive. In my world, navigation is one of the few things that is more important than fuel management - even on a sailboat.
If I were to install a fuel injection system with a return, I would also go find the tank valve from a dual tank Ford circa 1995 as they had the valve that did this.
If I could find the valve to do it, I would like to add a valve to the fill line so I could have two isolated systems. I haven't found one yet that I can conveniently fit in there.
Someday, I'll have to re-work the fuel vents to be gasohol friendly. That will probably happen the next time I have the fuel tanks down for a hose change and revision. This foamy stuff is a real pain.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] connected fuel tanks [message #169695 is a reply to message #169554] |
Tue, 15 May 2012 00:27 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Johnny Bridges wrote on Mon, 14 May 2012 11:30 |
I wouldn't do it, for the same reason you can't do it on low wing airplanes. Given a long hill, you stand the chance of pumping air whern there's still some gas left.
--johnny
'76 23' transmode norris
'76 palm beach
|
I wasn't going to comment but I see you said what I was thinking.
When you have two tanks and pump from both of them in parallel you get air for the first one to run dry instead of fuel from the one with many gallons left. This is not a good thing in an airplane or a GMC going up or down hill. You could be at the side of the side of the road or crash landed in a field with that arrangement.
I have run individual airplane tanks dry on many occasions and a GMC on one occasion. It sure is nice to switch to the other that is not sucking air and continue on my way.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] connected fuel tanks [message #171822 is a reply to message #169695] |
Sat, 02 June 2012 22:37 |
cbryan
Messages: 451
Registered: May 2012
Location: Ennis, Texas
Karma: 3
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Senior Member |
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A new guy has found out the interesting way that interconnected fuel tanks run out the same time. Bought the '78 Royale this March in California. Still listed by the way. It is the one with "too many options to list". 500 Cadillac, Rance Baxter EFI.....
While driving back after tire purchase, ran out of gas in the Mojave Desert the first time with 1/4 tank indicated on both tanks. Started to weave like NASCAR drivers and kept it running until the next exit, but it wouldn't run up the ramp to the gas station. Had to buy a gas can. attendant had schadenfreude, smirking at the guy not smart enough to keep gas in his vehicle.
Couldn't understand why flipping the switch wouldn't give me 7 more gallons.
Figured it out the second time in west Texas. Looked at the tank selector valve and found it bypassed. Got a few more miles by clamping off one hose with vise grips.
Must have the new sending units that won't indicate less than 1/4 tank. And PO might have followed some advice I saw somewhere to bend the pickup tube up off the floor to avoid the gunk. Being a former private pilot, don't agree with carrying around gasoline you can't use. Oh, yes, had a fuel spill on initial fillup from generator area and about the rear tank, so couldn't subsequently fill it up all the way, hence the guessing game on fillup. Keep filling and have the EPA charge me for a fuel spill, or call it good and get out of Dodge? The second time I ran out, shame on me. But, I was harboring ideas about the Accel EFI losing ground or power, as dash lights were flashing randomly also. That idea was born because of a safety feature of the EFI. After ten seconds of fuel pump on but no fuel pressure, computer cuts off the pump until cycling the ignition switch. Plenty to think about.
But I am thrilled with it, notwithstanding the problems, only a few I have related. It really has lots of power with the 3.42 ratio. One injector is flowing less, plug is white others dark brown. Increased the duty cycle on that one and emailed Rance Baxter. He was not encouraging in that the injector might stay on all the time. But, all plugs same color now, almost white. Closed loop, too. Some valve? exhaust manifold? bad fuel injector? noise when hot. New injectors are here but not installed. Lacking updated fire extinguishers. Have loads of respect for fire prevention for the motorhome.
Thank all for the excellent background and ideas to improve the motorhomes, it's amazing. I see that there's a lot of radio amateurs who are attracted to these money sinks. I am also a ham, NY0L. Prima Facie evidence of unbalance or worse.
Carey
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
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| Re: [GMCnet] connected fuel tanks [message #171830 is a reply to message #171822] |
Sat, 02 June 2012 23:55 |
bumpersticker
Messages: 60
Registered: February 2004
Location: Redondo Beach, CA
Karma: 0
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Cary:
One of your problems may be the tank selector valve. the ethanol based fuels tend to desolve the "O" ring in the valve. When the "O" ring goes the fuel pump will pull fuel from both tanks until one of the tanks sucks air. After one of the tanks sucks air it is all over until more fuel is added into the tanks. Your valve probably needs replaced.
Bob Cook
78 Birchaven
75 Avion (In work)
Redondo Beach, CA
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| Re: [GMCnet] connected fuel tanks [message #171886 is a reply to message #171844] |
Sun, 03 June 2012 12:43 |
cbryan
Messages: 451
Registered: May 2012
Location: Ennis, Texas
Karma: 3
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Senior Member |
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Thanks, Bob. I will look into that, but frankly the selector valve was already bypassed. I'm thinking of an all poly-armour two fuel pump setup. I'm also sweating making all those flares, never having done even one. Thinking of putting the fuel return line into the front tank vent line via a tee fairly high up near the gas filler tube connection, but lower than the separate rear tank vent line, and thus aux tank will always have extra gas coming back, when I run the rear tank dry, then the front tank will always have the extra gas going into it. That should keep me from doing the Emery Stora switch exercise when low on fuel.
I wonder just what undesirable things have been found in the bottom of tanks to prevent putting the pickup sock near the floor of the tank. I have even found gravel put into a bus gasoline tank where I worked, and after six months (could have been more than a year, inertia being what it is) when the weather was good enough to drop the tank, there was no trace of it. Tank nice and clean, too. (This was vandalism, of course, not deliberate on my part.) A wonder it disappeared. I can't tell you how much gravel was put into the tank before the vandal got bored. My impression was that it was a handful or so. The fuel filter was a good sized cartridge type. Never clogged. The gravel was like Cotton-eyed Joe. (Where did he come from, where did he go?)
Also saw somewhere for the GMC motorhome, the best anti-vapor lock setup may be to run the fuel pump on the outside of the frame, pressure line outside the frame to front left of engine, then teflon-stainless steel flex to fuel rail. Does anyone think this might be more dangerous due to the fuel lines and pump being more vulnerable to side impact? This is due to the frame not protecting the line and acting possibly as an anvil to break the fuel pump and line during a side impact event. Some vehicles have an impact-sensitive switch that turns off the fuel pump automatically with a big enough impact of any kind. Would that be worthwhile to incorporate?
Carey
Carey from Ennis, Texas
78 Royale, 500 Cadillac, Rance Baxter EFI.
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| Re: [GMCnet] connected fuel tanks [message #171906 is a reply to message #171886] |
Sun, 03 June 2012 17:37 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Carey,
I like your PolyArmour and two-pump solution, but not the return line
sharing the vent line. The opposing purposes are almost sure to cause
problems. The return line will always be full of liquid so that when
you're trying to fill the tanks, the first flow from the vent line
will kick off the nozzle. And do so repeatedly until the vent line is
purged of gasoline. At least that's what I'd expect. My return into
the bottom of the Aux tank through the drain plug may be SLIGHTLY
hazardous, but has been trouble-free for several years now. A 90*
elbow in the drain plug keeps the profile close to the tank; a shallow
steel channel "skid plate" bolted to the cross member just forward of
the tank protects the line and fitting from road hazards.
You may want to look at this diagram of how I wired my dual pumps:
http://www.gmcmhphotos.com/photos/data/5494/Dual_Fuel_Pump_Wiring.pdf
or
http://goo.gl/Lu9NJ
Note: I use a combiner and low oil pressure switch rather than the isolator.
As for the flares, having just gone through that exercise, I can tell
you that double flares on 3/8" PolyArmour are not easy -- unless,
perhaps, you have a VERY good tool which can grip the tube tightly.
When I re-do my plumbing soon, I'll be VERY glad that I did the supply
lines when I installed EFI. For the vent lines, I'll use compression
fittings. Some are willing to use those for pressure; I'm not.
It's probably not the greatest idea in the world, from a safety
standpoint, to run the fuel lines on the outside of the frame -- but I
still do it part of the way: My low pressure pumps are inside the
left rail just forward of the tanks; the high pressure filter and pump
are outside the left rail just behind the mud flap for the left front
wheel. That location was dictated by the convenience of the location
and the need to get away from the exhaust pipes. Hard line runs from
that pump to the rear lip of the engine hatch where it transitions to
SS/Teflon to connect to the throttle body.
If I had an acceleration-sensitive switch, I'd probably use it, but
I'm comfortable with the low oil pressure switch. Selecting an
acceleration switch for use on a 12,000 vehicle is not a matter of
just pulling one from a 3500# junkyard car, IMHO.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Sun, Jun 3, 2012 at 1:43 PM, Carey Bryan wrote:
>
>
> Thanks, Bob. Â I will look into that, but frankly the selector valve was already bypassed. Â I'm thinking of an all poly-armour two fuel pump setup. Â I'm also sweating making all those flares, never having done even one. Â Thinking of putting the fuel return line into the front tank vent line via a tee fairly high up near the gas filler tube connection, but lower than the separate rear tank vent line, and thus aux tank will always have extra gas coming back...
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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] connected fuel tanks [message #171912 is a reply to message #171886] |
Sun, 03 June 2012 17:45 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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G'day,
Some responses to your comments:
Re: making all those flares - you do not need flared fittings at every
junction, just at junctions where it would be desirable to make and break
the junction many times with no effect. You can use Parker Hannifin Ferrulok
or Swag Lok flareless fittings elsewhere.
Re: putting the pickup sock near the floor of the tank - remove the sock
completely and put a "strainer" on the outside before the filter.
Re: the best anti-vapor lock setup may be to run the fuel pump on the
outside of the frame - JimB installed a small Facet cube pump (1-4 psi out)
in the line that goes from the Aux tank to the fuel selector valve. It is
powered by the Main - Aux switch. When I switch to Aux it comes on and
INSTANTLY vapor lock problems stop. There is a down side to this pressurizes
the fuel lines up to the mechanical fuel pump. If there's any leaks fuel
will escape. Also if the diaphragm in the mechanical fuel pump is weak it
could tear and the Facet would pump the crankcase full of gasoline and the
results would be catastrophic for the engine. I have had this pump in place
for several three thousand mile trips with no ill effect. If fact I wasn't
careful once and the Main - Aux switch in the Aux position for several
hundred miles.
Regards,
Rob M.
-----Original Message-----
From: Carey Bryan
Thanks, Bob. I will look into that, but frankly the selector valve was
already bypassed. I'm thinking of an all poly-armour two fuel pump setup.
I'm also sweating making all those flares, never having done even one.
Thinking of putting the fuel return line into the front tank vent line via a
tee fairly high up near the gas filler tube connection, but lower than the
separate rear tank vent line, and thus aux tank will always have extra gas
coming back, when I run the rear tank dry, then the front tank will always
have the extra gas going into it. That should keep me from doing the Emery
Stora switch exercise when low on fuel.
I wonder just what undesirable things have been found in the bottom of tanks
to prevent putting the pickup sock near the floor of the tank. I have even
found gravel put into a bus gasoline tank where I worked, and after six
months (could have been more than a year, inertia being what it is) when the
weather was good enough to drop the tank, there was no trace of it. Tank
nice and clean, too. (This was vandalism, of course, not deliberate on my
part.) A wonder it disappeared. I can't tell you how much gravel was put
into the tank before the vandal got bored. My impression was that it was a
handful or so. The fuel filter was a good sized cartridge type. Never
clogged. The gravel was like Cotton-eyed Joe. (Where did he come from,
where did he go?)
Also saw somewhere for the GMC motorhome, the best anti-vapor lock setup may
be to run the fuel pump on the outside of the frame, pressure line outside
the frame to front left of engine, then teflon-stainless steel flex to fuel
rail. Does anyone think this might be more dangerous due to the fuel lines
and pump being more vulnerable to side impact? This is due to the frame not
protecting the line and acting possibly as an anvil to break the fuel pump
and line during a side impact event. Some vehicles have an impact-sensitive
switch that turns off the fuel pump automatically with a big enough impact
of any kind. Would that be worthwhile to incorporate?
Carey
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GMCnet mailing list
Unsubscribe or Change List Options:
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] connected fuel tanks [message #171928 is a reply to message #171912] |
Sun, 03 June 2012 21:57 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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""There is a down side to this pressurizes
the fuel lines up to the mechanical fuel pump. If there's any leaks fuel
will escape. Also if the diaphragm in the mechanical fuel pump is weak it
could tear and the Facet would pump the crankcase full of gasoline and the
results would be catastrophic for the engine. I have had this pump in place
for several three thousand mile trips with no ill effect. If fact I wasn't
careful once and the Main - Aux switch in the Aux position for several
hundred miles.
Regards,
Rob M.
""
I use my GMC in temperatures of 100 F and above on a routine basis. At altitude I ocassionally start to feel vapor lock and I hit the switch for the electric fuel pump and all is well in a matter of seconds. After that I shut the pump off and continue my trip with the mechanical pump. After all my years around cars, I have never seen nor experienced ruptured mechanical pumps and the horrific crankcase full of fuel syndrom. I hear anecdotal stories about that, but so do I about tornados in Phoenix.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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