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#26 |
Registered User
Join Date: Nov 2009
Location: Haines City FL
Posts: 461
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Re: Dual tanks not switching
Actually disconnect the valve first and try to start the truck and see what you get. Then You can disconnect all the wires to the valve, connect 12 volts and ground to the green and light green wires then reverse polarity and it should switch. if it does not, then you have something wrong with the valve.... I would have Bench tested it before i put it on.. You should have at least heard or felt something.
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#27 | |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
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Re: Dual tanks not switching
Quote:
The senders are a separate circuit.
__________________
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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#28 |
Registered User
![]() Join Date: Jan 2013
Location: Alamosa, CO
Posts: 19
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Re: Dual tanks not switching
I had trouble with my 78 dually tank system for 13 years before I wised up and went with the old valve setup. It wasn't a hard project and it sure beats laying on the side of the highway in the winter with snow coming down and semis spraying slush and road salt in your face.
A year after I bought the truck I changed all of the wiring, switch, tank selector, fuel lines, the works. It lasted for three years of work and then started the same old garbage. The last time it quit on me I was pulling a really heavy load way out of town and it stopped on a two lane without an emergency lane. It was around 98 degrees that day and the truck just happened to stop on an ant hill. Bad day to say the least! I can get the brass valves for the pre 73 model trucks for fairly cheap (not the $150 that the parts houses want) and can get them to you if you want to go that route. You will need two, one for the feed lines and one for the return lines. I put them just in front of the seat where all I have to do is reach down and turn the handles when the gauge is reading low. Really easy fix! Took me and my kids an afternoon to switch over the system. It was well worth it! The only thing the switch in the dash does now is to let me know how much fuel is in each tank. Hope this helps. Let me know if you are interested and I will get you a price quote with your address. |
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#29 |
Registered User
Join Date: Aug 2012
Location: Ct.
Posts: 43
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Re: Dual tanks not switching
Disregard the pink wires to the senders they are not used as ground for the valve as I thought, they are for the gauge only, I was wrong and did not mean to confuse you more.
Bench test your valve again, go back to your d and e terminals. As hatzie stated the 2 green wires switch polarity meaning when you hit your switch one acts as a power wire while the other acts as a ground completing the circuit and vice versa when switched to the opposite tank. Put power to d and ground e, then switch your power to e and ground to d, if the valve is working properly you should hear it switch over. |
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#30 |
Registered User
Join Date: Feb 2013
Location: LaGrange, OH
Posts: 17
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Re: Dual tanks not switching
I tried finding the buss bar but am having troubles finding it. I know you said it was by the e brake but not entirely sure where it is.
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__________________
Ol' Red. 1985 GMC Sierra Classic 1500 2wd 305/th350/2:73 rear ![]() "never miss a good opportunity to shut up" "if you look back at your work and you aren't proud to you say did it then you better go back and do it over" "don't talk bad about farmers with your mouth full" |
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#31 |
Registered User
Join Date: Jul 2011
Location: back 40, bc
Posts: 3,817
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Re: Dual tanks not switching
here you go, left side under the wire in the grommet
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#32 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
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Re: Dual tanks not switching
A couple extra grounds there.
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__________________
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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#33 |
Registered User
Join Date: Feb 2013
Location: LaGrange, OH
Posts: 17
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Re: Dual tanks not switching
Today I had a chance to look at the truck again. The ground at the buss bar is good. I found out something pretty interesting though. At my switch I took my volt meter and get 12v from the pink to black. Power to ground. When I go pink to either green wire I only get 4v. I understand that whatever green isn't getting power the other is ground. I am jus trying to figure out why it would only be 4v. When I did this I had the switch off the connector. Any ideas?
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__________________
Ol' Red. 1985 GMC Sierra Classic 1500 2wd 305/th350/2:73 rear ![]() "never miss a good opportunity to shut up" "if you look back at your work and you aren't proud to you say did it then you better go back and do it over" "don't talk bad about farmers with your mouth full" |
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#34 | |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
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Re: Dual tanks not switching
Quote:
Either the valve is weakly conducting to a ground (the gauge circuit on Terminals A B C of the valve) or the wires have a weak short to ground via damaged insulation. My money would be on the valve itself...
__________________
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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#35 |
Registered User
Join Date: Feb 2013
Location: LaGrange, OH
Posts: 17
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Re: Dual tanks not switching
This is sort of an old thread but just wanted to let everyone know what the problem was. My switch, valve and wires all seemed to be working just fine. A new valve was the part that fixed it. The switch was. I did continuity checks on it and made sure i was getting the proper voltage to the valve which i was however just for fun I took some wires and used them in place of the switch and the valve worked just fine. I bought a new switch and it fixed it. I have no idea how the switch was bad even though it had the volts going through it but it was definitely bad.
__________________
Ol' Red. 1985 GMC Sierra Classic 1500 2wd 305/th350/2:73 rear ![]() "never miss a good opportunity to shut up" "if you look back at your work and you aren't proud to you say did it then you better go back and do it over" "don't talk bad about farmers with your mouth full" |
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#36 |
Registered User
Join Date: Oct 2013
Location: HOUSTON
Posts: 355
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Re: Dual tanks not switching
thanks for the update!
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#37 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
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Re: Dual tanks not switching
Thanks for the update. The switch is the most common failure point. The valve is big bucks but the AC Delco # D7089C switch is cheap.
This part # is listed as 1987-91 RV series TBI only. It's an ON-ON switch, is easier to use, and will last longer than the "right" momentary switch. It works just fine for all 1981-1991 CK RV dual tank trucks.
__________________
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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#38 |
Registered User
Join Date: Oct 2013
Location: Winfield KS
Posts: 489
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Re: Dual tanks not switching
Bringing this back from the dead to aid in helping fix my truck
__________________
88' Chevy V30 3+3 4x4 Dually 454 TBI/NV4500/NP205 |
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#39 |
Account Suspended
Join Date: Jun 2011
Location: Des Moines, IA.
Posts: 4,143
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Re: Dual tanks not switching
The ON-ON switches are the ones to use. I'd dis-regard using the other ones too. I just built all new dual tank harnesses for my project and now have those fuel harnesses available so now at least people can swap out their entire 25+ year old wiring if need be.
Last edited by gmachinz; 08-09-2016 at 06:58 PM. |
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#40 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
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Re: Dual tanks not switching
He has an 88 TBI so that's already the right switch... but really it's the only one to use with the motor valves period. The intern engineer that thought the momentary switch was a good idea should be beaten senseless with wet spaghetti.
__________________
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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