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#176 | |
Registered User
Join Date: Sep 2019
Location: Scottsdale Arizona
Posts: 114
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Re: 1973-1991 Dual fuel tank systems theory of operation
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#177 |
Registered User
Join Date: Sep 2019
Location: Scottsdale Arizona
Posts: 114
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Re: 1973-1991 Dual fuel tank systems theory of operation
I went ahead and replaced the six port valve today, just to make sure it wasn't a problem with the valve itself. As I was connecting the six lines, I double checked the paperwork/diagram and the routing of the lines to make sure everything was in the correct spot.
Right now, both my tanks are fairly full. I filled them a few weeks ago, drove maybe 20 miles, and since then has been just idling in the driveway a total of maybe 20 minutes - so both the tanks are still pretty full. I don't have a fuel gauge hooked up just yet. When running on one tank, if given long enough, the opposite tank starts spewing gas, as if the returns were backwards but they're not. If I switch tanks when the spewing begins, it will stop spewing after a second, and after awhile start spewing from the opposite tank The strange part is that, before I swapped the valve today, the old valve and lines had been in place for almost three years with no problems, even with both tanks completely full. Nothing ha changed between now and then except for a complete rewire of the truck, selector switch included. Tanks, senders, straps, fuel lines and regulator were all replaced at the same time about three years ago. Anyone have any ideas? |
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#178 | |
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Join Date: Dec 2011
Location: Yuma Arizona
Posts: 1,526
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Re: 1973-1991 Dual fuel tank systems theory of operation
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#179 |
Registered User
Join Date: Sep 2019
Location: Scottsdale Arizona
Posts: 114
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Re: 1973-1991 Dual fuel tank systems theory of operation
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#180 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,953
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Re: 1973-1991 Dual fuel tank systems theory of operation
The charcoal canister isn't a big deal to plumb and it isn't a performance hit.
It's only three connections.
__________________
1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
And please let us know if and how your repairs were successful. |
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#181 | |
Registered User
Join Date: Sep 2019
Location: Scottsdale Arizona
Posts: 114
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Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
How would a charcoal canister keep gas from spewing out of the tanks? |
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#182 |
Registered User
Join Date: Sep 2019
Location: Scottsdale Arizona
Posts: 114
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Re: 1973-1991 Dual fuel tank systems theory of operation
I spent a bit of time after work today troubleshooting. I started the truck up running on the left tank, and removed the gas cap. After a few minutes, I can see the gas level rising up through the fill port, until eventually it starts spilling out the fill port on the left tank.
Once that happened, I removed the power wire from the selector switch that feeds the left tank, so only the right tank was hooked to the switch, and started up again. Same result I disconnected the two vents where they tee together and plugged them off to rule out fuel somehow crossing from one tank to the other via the breather hose, and same result. Finally, just for ****s and giggles, I swapped the return lines at the fuel selector valve, and same result. I have no idea wtf is happening. |
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#183 | |
*************
![]() Join Date: Apr 2005
Location: Pensacola, FL
Posts: 17,846
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Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
__________________
Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3 |
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#184 |
Registered User
Join Date: Sep 2019
Location: Scottsdale Arizona
Posts: 114
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Re: 1973-1991 Dual fuel tank systems theory of operation
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#185 |
*************
![]() Join Date: Apr 2005
Location: Pensacola, FL
Posts: 17,846
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Re: 1973-1991 Dual fuel tank systems theory of operation
I would completely disconnect one of the tanks feed and return line and then power up the other side. This should help you narrow it down.
__________________
Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3 |
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#186 |
Registered User
Join Date: Sep 2011
Location: Canada
Posts: 86
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Re: 1973-1991 Dual fuel tank systems theory of operation
Great info in here! It is nice to know I can ditch the earlier problematic switch with the simple 2-position switch from the newer trucks. I'm hoping to get my second tank operational sometime this year. I have a feeling I should pick up the switch and a new valve at minimum, then go from there. The entire 10 years I have owned the truck I am not even sure what is in the left tank if anything lol.
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'84 Chevy Custom Deluxe 10 "Frankenstein" http://67-72chevytrucks.com/vboard/s...d.php?t=690587 '69 Chevy C10 |
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#187 | |
*************
![]() Join Date: Apr 2005
Location: Pensacola, FL
Posts: 17,846
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Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
__________________
Rob - https://www.instagram.com/hart_rod_c10 As Iron Sharpens Iron, So One Man Sharpens Another. Proverbs 27:17 FOR SALE: DBW pedal bracket - http://67-72chevytrucks.com/vboard/s...d.php?t=651123 FOR SALE: Hood Brackets http://67-72chevytrucks.com/vboard/s...d.php?t=679945 1987 Silverado SWB - 34.5K original miles http://67-72chevytrucks.com/vboard/s...d.php?t=801834 1969 SuperBurb - http://67-72chevytrucks.com/vboard/s...d.php?t=200387 1968 Farm truck - http://67-72chevytrucks.com/vboard/s...d.php?t=358692 1968 SWB - http://67-72chevytrucks.com/vboard/s...d.php?t=551258 1948 Chevy - http://67-72chevytrucks.com/vboard/s...=122164&page=3 |
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