Home » Public Forums » GMCnet » Don't Do This!
| Don't Do This! [message #366545] |
Tue, 07 September 2021 13:01  |
LNelson
Messages: 335
Registered: December 2008
Location: Springfield, MO
Karma: 0
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This is for a newer owner. Many decades ago, I discovered (with my Palm Beach), that we really don't want to switch from the Main Tank to the Aux Tank just after you have fueled up. That coach, and my current E-II, both cough and fart and hardly can produce any power, until switching back to the Main until more the main is emptied. Why did I switch it to the AUX, you are asking yourself......well, I reached down to switch on the fuel pump and instead switched the fuel TANKS. I was also getting into hairy hill country and really struggling to climb even modest grades. Wondering what to do, thinking I got a load of bad gas (remember, I had just refueled)....I was wondering if I had a serious problem in the worse possible location. My pilot training told me to switch tanks, and then I noticed that I ALREADY HAD DONE THAT (by mistake). I switched back to the Main, and the old iron horse smoothed out and I was on my way.
No, I never knew why both of my coaches did this. But they did and DO. Word to the wise, run your main tank down before switching. I usually go to 1/2. Just thought it might help someone smarter than me.
Larry Nelson Springfield, MO
Ex GMC'er, then GM Busnut
now '77 Eleganza ARS WB0JOT
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| Re: Don't Do This! [message #366546 is a reply to message #366545] |
Tue, 07 September 2021 13:18  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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I am believer that you can switch whenever you want. I think that keeps the fuel selector working. You don't use it for a while, your fuel selector valve gets sticky.
when I had a carb and an electric pump on the aux side, everytime I started the coach, I switched to Aux, hear the pump run a little. fire engine then switch to main. Usually kept it on main unless I had experience of vapor lock or thought I had potential for vapor lock.
now that I run 100% electric pumps, 2ea, 1 for each tank on my EFI system. I still switch between the two, in belief that the more you use them, the better they are.
almost every GMC I come across, no two are the same anymore. different routing of lines and vents. Different fuel pumps and wiring. many different places people stick fuel filters in. If they are the same, it is because it has 45 year old parts that are gunked up from non use.
now what Every GMC'r should take some time and study this slide, so they understand what hills and fuel can do in the GMC:
http://gmcmotorhome.info/tank.html
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
[Updated on: Tue, 07 September 2021 13:20] Report message to a moderator |
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| Re: Don't Do This! [message #366547 is a reply to message #366545] |
Tue, 07 September 2021 13:36 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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When the tanks get a bit low it is best to switch to the main going up hill and the auxiliary going down hill because the gas will move from one tank to the other.other then that I never had a problem.
Roy Keen
Minden,NV
76 X Glenbrook
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| [GMCnet] Re: Don't Do This! [message #366548 is a reply to message #366547] |
Tue, 07 September 2021 14:02 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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I prefer to use the aux tank and runit down from time to time as it keeps
both tanks with rather fresh
On Tue, Sep 7, 2021 at 11:37 AM roy keen wrote:
> When the tanks get a bit low it is best to switch to the main going up
> hill and the auxiliary going down hill because the gas will move from one
> tank
> to the other.other then that I never had a problem.
> --
> Roy Keen
> Minden,NV
> 76 X Glenbrook
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Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
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| Re: Don't Do This! [message #366553 is a reply to message #366545] |
Tue, 07 September 2021 19:16 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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I guess every coach is different, but I've NEVER experienced any issue due to changing the tank selector valve at ANY level of fuel. I do it often due to the having my electric pump switched with my aux tank.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| [GMCnet] Re: Don't Do This! [message #366560 is a reply to message #366553] |
Tue, 07 September 2021 20:04 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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The original selector valve are deteriorated due to age and ethanol and
need to be replaced with newer one.
On Tue, Sep 7, 2021 at 5:17 PM Carl Stouffer wrote:
> I guess every coach is different, but I've NEVER experienced any issue due
> to changing the tank selector valve at ANY level of fuel. I do it often
> due to the having my electric pump switched with my aux tank.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
--
Jim Kanomata ASE
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.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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| [GMCnet] Re: Don't Do This! [message #366583 is a reply to message #366553] |
Wed, 08 September 2021 12:14 |
lcoldren
Messages: 28
Registered: March 2004
Karma: 0
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If your fuel supply system is in good condition you will have no problem switching between tanks. Two problems that I have experienced are the original tank selector solenoid valve failed with the rubber tip frozen blocking the Aux tank line. The other was the sock in the Aux tank was plugged. If you are using a one-way valve with electric fuel pumps, be sure the flow is in the correct direction. The Aux tank should function the same as the main tank as far as fuel supply, they are common above a 1/4 tank. The GMC always presents many learning opportunities.
Larry Coldren
1974 Canyon Lands
Fort Collins CO
________________________________
From: Carl Stouffer
Sent: Tuesday, September 7, 2021 06:16 PM
To: gmclist@list.gmcnet.org
Subject: [GMCnet] Re: Don't Do This!
I guess every coach is different, but I've NEVER experienced any issue due to changing the tank selector valve at ANY level of fuel. I do it often
due to the having my electric pump switched with my aux tank.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Re: Don't Do This! [message #366598 is a reply to message #366583] |
Wed, 08 September 2021 15:46 |
LNelson
Messages: 335
Registered: December 2008
Location: Springfield, MO
Karma: 0
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Take my words with a grain of salt, This has occurred with both coaches and with no known mods to the fuel plumbing. Feel free to disregard my comments. I always assumed it was something similar to the old Bonanzas with the pressure carbs. You ALWAYS ran the main tank an hour before switching to the aux tank as the pressure carb fed 2 gph back to the main. Since this happened to me Monday climbing the hills of AR I thought it worthy to bring up. However it appears my two coaches are the only two that suffer from this.
Larry Nelson Springfield, MO
Ex GMC'er, then GM Busnut
now '77 Eleganza ARS WB0JOT
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| [GMCnet] Re: Don't Do This! [message #366600 is a reply to message #366598] |
Wed, 08 September 2021 15:55 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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As I've mentioned before, the return from my EFI/Accumulator is into the
drain on the Aux tank. That has, to me, a major advantage: Unless I've
got that tank's independent pump selected, I KNOW there's fuel in it up to
the between-tanks pipe. With Aux selected, I can run the system "dry" down
to the pickup tube in the Aux, because any gas the TB doesn't accept, goes
right back to that tank.
Ken H.
On Wed, Sep 8, 2021 at 4:46 PM Larry Nelson
wrote:
> Take my words with a grain of salt, This has occurred with both coaches
> and with no known mods to the fuel plumbing. Feel free to disregard my
> comments. I always assumed it was something similar to the old Bonanzas
> with the pressure carbs. You ALWAYS ran the main tank an hour before
> switching
> to the aux tank as the pressure carb fed 2 gph back to the main. Since
> this happened to me Monday climbing the hills of AR I thought it worthy to
> bring up. However it appears my two coaches are the only two that suffer
> from this.
> --
> Larry Nelson Springfield, MO
> Ex GMC'er, then GM Busnut
> now '77 Eleganza ARS WB0JOT
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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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] Re: Don't Do This! [message #366627 is a reply to message #366600] |
Thu, 09 September 2021 09:34 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Ken Henderson wrote on Wed, 08 September 2021 16:55As I've mentioned before, the return from my EFI/Accumulator is into the drain on the Aux tank. That has, to me, a major advantage: Unless I've got that tank's independent pump selected, I KNOW there's fuel in it up to the between-tanks pipe. With Aux selected, I can run the system "dry" down to the pickup tube in the Aux, because any gas the TB doesn't accept, goes right back to that tank.
Ken H.
Ken,
If by the drain for the auxiliary tank, you mean the plug in the bottom I might caution some about that. I will admit that I know my coach went to Mexico with the prior owners, but I can see strike damage to both tanks and the transmission pan. None are huge, but they also aren't a pipe elbow sticking down another inch plus.
I do have a suggestion. If you are working on the fuel plumbing and choose to to the High T Mod (That makes fueling go so much easier), it would be simple to place a T in the fill vent line to the auxiliary tank and be done right there.
We use a different and so far very successful fuel management plan. We run on the main tank until the indicator says about half, then we change to the auxiliary tank. This has two values. First, it means we are burning off the old fuel that might still be in the auxiliary tank. Second, we will still have the bottom half that we can use some of the run the generator if we need to. So far, this has worked out well. I also have to include that I replaced both sending units a few years back and they are both still working as hoped.
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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| [GMCnet] Re: Don't Do This! [message #366635 is a reply to message #366632] |
Thu, 09 September 2021 10:06 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Matt,
Yes, I DO use the drain plug in the bottom of the Aux tank for my return
line. But that line and low-profile elbow are well protected by a thick
custom steel guard. I'm not saying it's indestructible, but if that goes,
the bottom of the tank might well have gone anyway. After 10+ years of
nationwide travel, it shows no sign of damage. :-)
Ken H.
On Thu, Sep 9, 2021 at 10:55 AM Matt Colie wrote:
> Larry wrote on Thu, 09 September 2021 10:47
>> I have return fuel going to the reserve tank through the tank drain
> plug. Then created a angle iron covering the fuel line to protect it from
> road
>> debris.
>>
>> http://www.gmcmhphotos.com/photos/gmcmi/p68345-efi-fuel-regulator.html
>
>
> What a great idea.
>
> 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
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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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] Re: Don't Do This! [message #366638 is a reply to message #366627] |
Thu, 09 September 2021 10:42 |
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Richard RV
Messages: 631
Registered: July 2012
Location: Full-timer for 12 years, ...
Karma: -17
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Senior Member |
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Matt Colie wrote on Thu, 09 September 2021 07:34
I do have a suggestion. If you are working on the fuel plumbing and choose to to the High T Mod (That makes fueling go so much easier), it would be simple to place a T in the fill vent line to the auxiliary tank and be done right there.
I like that. Two birds with the one stone. Your High T vent plumbing effectively adds another "home run" vent line by separating the common.
I'm not clear on how much fuel is actually returned to the tank. Would a Y be better than a T fitting to help direct the fuel?
Richard
'77 Birchaven TZE...777;
'76 Palm Beach under construction;
‘76 Edgemont waiting its turn
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