Fuel tanks [message #358684] |
Wed, 16 September 2020 06:48 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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So kinda going thru my to do list on my motorhome. Being that the Covid numbers were clicking up around KC we decided to lay low around the house.
So thus all the projects on the motorhome.
The next project is to work on the fuel tank system. Never been confident on the gas gage. I had a mechanic drop the tanks and replace all the hoses. At that time he told me about only one sending unit working, so he set it up to have the rear sender work. The instruction to me was that the fuel gage 1/2 tank reading was actually be a 1/4 tank. Now I seem to be running out of gas at just above 1/2 tank so plan on replacing the tank selector valve, but in re-reading the info online on the subject I ran across this.
I'm having senders go out more frquently and with the crappy action of the new senders available, I have been opening up the senders, cleaning up the windings of the resister coil resetting the tension on the wiper and checking connections on the terminal to make the old senders work again. Have been pretty successful in getting at least one of the 2 senders working. In reality you only need one sender (preferrably in the rear tank) to work. Both senders read the same fuel level until the tank with the sender goes below 1/4 tank. I would never run a coach below 1/4 tank-- they are too heavy to push! If you watch the odometer and not go below 1/4 tank as much as possible, one good sender will do ya. On fuel injected coaches, I toe a crossover between the drains of the tanks to allow sharing of fuel right to the bottom which actually negates the need for 2 senders. If the FI system dumps it's pressure into the fill rail, you could draw one tank
totally dry without the lower crossover line.
I am wondering having this lower crossover hose to combine both tanks would be my best solution? I am hoping this will be so I can get a reliable fuel level reading and use most of my fuel capacity. Seems to be a simple and slick solution to all this. If so then not seeing a need for fuel selector valve?
Thanks,
Tom
Tom Geiger
76 Eleganza II
KCMO
[Updated on: Wed, 16 September 2020 06:51] Report message to a moderator
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Re: Fuel tanks [message #358686 is a reply to message #358684] |
Wed, 16 September 2020 07:42 |
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RF_Burns
Messages: 2277 Registered: June 2008 Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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Tom,
I have EFI so running low on fuel is something I don't want to do. I also don't think of the tanks as Main & Aux, more like 2 tanks, front and rear.
From experience I find that once the fuel level gets below 1/2, more fuel tends to stay in the front (Aux) tank than in the rear (Main) tank. This is proven in these diagrams on Gene's site:
http://gmcmotorhome.info/tank.html
Because of the forward position of the fill ports, fuel tends to move to the front tank when going down-hill and when braking and more significantly when braking and going downhill. In the latter case I've seen 1/2 tank reading on level ground turn to Empty in rear (Main) and 3/4 reading on front (Aux) tank.
My EFI fuel return goes into the fill tube at the front. I've also noted that when running at 1/4 tank and below, level ground on the front (Aux) tank, the return fuel tends to run past the front and into the rear (main) tank. So my front tank gets pumped down fast and the rear fills up. So when I get low I'm watching the gas gauge closely and changing back and forth wherever the gauge says the fuel is. So I can't imagine running on one tank sensor. I need both to see where if the fuel is!
So my rule of thumb is once I get to 1/2 tank reading, I'm looking to fill up with fuel. That's about 200-250 miles of driving and 4 to 5 hours of sitting. My butt is numb and my bladder is full! so I need a break too.
I know it bothers some that there is still 1/2 tank left that they "are not using". But that 1/2 tank is about 20 usable gallons which is about $50 in fuel. The cost to fix it so you can reliably and consistently get that last $50 in fuel is going to cost you much more than $50. Its still there if you need it, you just need to be more careful about watching your tank levels when going that low.
I did see a product which was like a mat kinda filter. It was laid out in the tank and held fuel like a sponge bringing it to the fuel pickup from wherever it was in the tank. But it was expensive and the largest at about $400 each was still not big enough for our tanks.
You mentioned about replacing your fuel selector valve. If you have EFI, I would suggest instead installing dual fuel pumps. The cost of the second fuel pump is about the same as the cost of the selector valve and it gives you redundancy in your fuel pumps.
http://www.gmcmhphotos.com/photos/g7210-dual-fuel-pumps.html
One last thing, the thought of that tube between the tank drains always makes me nervous for road debris hitting it. Make sure you have a study shield to protect it from tire carcasses etc hitting it!.
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: Fuel tanks [message #358687 is a reply to message #358684] |
Wed, 16 September 2020 08:36 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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Bruce, thanks for the write up on this. Solid logic in it. It clears up the issue with actual behavior of the gas in the tanks in application which is very good. I’ve been seriously considered going over to a EFI system but not at this point. I’m hoping to do something about my all electric fridge first and then maybe next year look at the EFI systems. I was considering the small resevior tank system to avoid all the return line setup to the gas tanks. I also was looking at a FI-Tech system but had read some breakdown failures from some which brings in to question of its dependability.
But it sounds like joining the tanks with a lower flow hose is not ideal and restoring original fuel system is recommended in any setup. So I can proceed in that direction.
Thanks Bruce,
Tom
Tom Geiger
76 Eleganza II
KCMO
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Re: Fuel tanks [message #358717 is a reply to message #358684] |
Thu, 17 September 2020 05:05 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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Senior Member |
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One more question on the fuel tanks. Anyone have a good diagram of the fuel hose and wiring of the senders? Just need a good understanding of what it should be when I lower the tanks. I have no idea what my mechanic did when he worked on them.
Thanks,
TG
Tom Geiger
76 Eleganza II
KCMO
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Re: Fuel tanks [message #363093 is a reply to message #358684] |
Sat, 27 March 2021 16:29 |
tgeiger
Messages: 518 Registered: February 2006 Location: kansas city
Karma: -1
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Senior Member |
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Perfect info guys, much appreciated. Will be digging into this soon. These pointers sure help!
TG
Tom Geiger
76 Eleganza II
KCMO
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