![]() |
![]() |
#101 |
chevy truck fan
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,988
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Hatzie,
THANK YOU AGAIN for your time and sharing of your knowledge. I am currently looking to install my new '87 tbi tanks with installed AC DELCO EP 381 fuel pumps I also have a replacement AC Delco fuel valve (U7000) and a replacement WVE pigtail connector. I am wondering if you might share what/how I should connect the pump wires? the pumps have the "factory" weather pack connectors on them? again thank you for your knowledge and time!! the truck is 1986 2wd swb silverado with factory duel tanks doing a 4.8LS swap. |
![]() |
![]() |
![]() |
#102 |
Registered User
Join Date: Jan 2002
Location: Henderson, NV
Posts: 358
|
Re: 1973-1991 Dual fuel tank systems theory of operation
I have a 1987 Chevy pickup with dual tanks. The plug on the dual tank switch has been cut off and I have 4 wires hanging out of the dash. tan, tan w/white stripe black w/white stripe and gray.Does anyone know how they go onto the new switch i bought?
__________________
1980 Chevy Shortbed Pickup 1969 Z28 engine Turbo 350 Last edited by Mixup; 09-30-2020 at 03:41 PM. |
![]() |
![]() |
![]() |
#103 |
I'm just glad to be here!
Join Date: Jan 2008
Location: Longview, TX
Posts: 4,788
|
Re: 1973-1991 Dual fuel tank systems theory of operation
There is a diagram on Post #76. It has the info you are looking for on the switch.
__________________
Karl ![]() 1965 Chevy Stepside(Grandpa's Old Blue) and (July 2015 Shop Build!)(2020, the Saga Continues) http://67-72chevytrucks.com/vboard/s...d.php?t=372424 The LST Challenge: http://67-72chevytrucks.com/vboard/s...=1#post7812257 Korbin's 1st Square: "Sunburn" http://67-72chevytrucks.com/vboard/s...d.php?t=418618 1985 GMC Sierra: "White Trash", Korbin's 2nd now... http://67-72chevytrucks.com/vboard/s...d.php?t=632305 Henry - 1984 Chevrolet, Owen's 1st Square |
![]() |
![]() |
![]() |
#104 | |
Registered User
Join Date: Dec 2011
Location: Yuma Arizona
Posts: 1,526
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
|
|
![]() |
![]() |
![]() |
#105 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
|
Re: 1973-1991 Dual fuel tank systems theory of operation
The stock TBI relay on the firewall is wired inline with the incoming power to the NL2 option rocker switch in the dash. The relay GM used is a Metripak sealed 5 terminal relay. Electrically it's the same as your garden variety Bosch mini ISO relay but it's more compact and the terminals are not open to the elements. You have an electromagnet on terminals D & F that pulls a Common terminal E switch reed from the Normally Closed C terminal to the Normally Open A terminal. The electromagnet receives power from the ECM and ground from the chassis. The relay switches power to the fuel pump to protect the ECM driver circuit from the fuel pump motor startup inrush current, motor running current, and shorts in the fuel pump wiring. I believe terminals D & F are Metripak 150 and A C & E are higher current Metripak 280 terminals. The relay, oil pressure switch, and the ECM perform an important safety function. When the engine is running the ECM gets pulses from the ignition module and switches on the fuel pump relay along with enabling injector pulses. As you can see in the diagram the oil pressure switch has open contacts to power the fuel pump once the oil pressure rises and cut power to the fuel pump(s) when the engine stops rotating. If you have an accident, and the engine shuts off, the fuel pumps will stop running as well rather than feeding a fire. Not all early fuel injected vehicles had this safety feature. The accident scenes were extremely unpleasant. The RED wire test terminal allows you power the fuel pump(s) without actuating the relay.
__________________
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. Last edited by hatzie; 04-09-2021 at 09:59 AM. |
![]() |
![]() |
![]() |
#106 |
chevy truck fan
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,988
|
Re: 1973-1991 Dual fuel tank systems theory of operation
hatzie, I tried to skim through and find out, but can you tell "us" again which tank (side) is the main tank? and which is the aux. tank? I am trying to do this on my '86 LS swap now... still!
![]() thanks!!! ![]() |
![]() |
![]() |
![]() |
#107 |
Registered User
Join Date: Dec 2011
Location: Yuma Arizona
Posts: 1,526
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Main is driver side (from the seated POV).
|
![]() |
![]() |
![]() |
#108 | |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
Why? The motorized valve stays where it comes to rest and doesn't change again til you select the opposite tank. Select the RH tank with the valve plugged in and hook the RH tank hoses to the side that's open through the valve. Or select the LH tank and do it that way. AUX and MAIN are really only meaningful with the 1980 and prior solenoid type valves. AUX is the tank selected in the powered valve position MAIN is the unpowered position. AUX is entirely dependent on the way the valve was hooked up by the last guy that was working on it. I've seen LH AUX and RH AUX tanks. I believe the 1973-1980 primary tank was the LH tank but don't quote me on that. My single tank 1974 had the fuel door on the LH side of the bed. Yes the fuel door bed came off a later truck. No I don't know whether one of the previous five owners moved the tank from the RH to the LH side of the truck.
__________________
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. Last edited by hatzie; 04-13-2021 at 08:29 PM. |
|
![]() |
![]() |
![]() |
#109 |
chevy truck fan
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,988
|
Re: 1973-1991 Dual fuel tank systems theory of operation
hatzie, thanks ... that does make sense. I have the '87 switch (for my LS swap) I decided to make the driver tank the main and will run feed and return lines accordingly.
in general I just want to publicly thank you for your time and knowledge that you share on this board. I am sure that I am not alone when I tell you thank you.... ![]() |
![]() |
![]() |
![]() |
#110 |
chevy truck fan
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,988
|
Re: 1973-1991 Dual fuel tank systems theory of operation
hatzie, I just want to make sure that I am thinking correctly. on the EP381 pump (and sender unit) the purple wire(at gas tank) connects to the sending unit wire for the appropraite tank sending unit wire on the switch valve 5 wire harness? and the grey wire connects to the appropriate power wire on the switch valve harness?
thanks! |
![]() |
![]() |
![]() |
#111 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Sounds right.
__________________
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. |
![]() |
![]() |
![]() |
#112 |
chevy truck fan
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,988
|
Re: 1973-1991 Dual fuel tank systems theory of operation
|
![]() |
![]() |
![]() |
#113 | |
Registered User
![]() Join Date: Jul 2015
Location: Phoenix, AZ
Posts: 1,335
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
In any event, I'd like to learn a bit more about the system on my truck, as I'll be shortening the bed and replacing the 20 gal tanks with 16 gal tanks. I want to may sure my system works correctly, as I'm going to need both thanks with a 454. To what site is being referred above? Does anyone have the link or more info? Thanks. |
|
![]() |
![]() |
![]() |
#114 | |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
http://forum.73-87chevytrucks.com/sm...0970#msg270970 ^^ This is the thread I was referencing. Not a lot of information there but it's the most I've seen anywhere.. My understanding, never having owned one myself, is the 73-75 cable system is a cable operated valve under the truck with some kind of switch built into the dash assembly to select which sender was connected to the fuel gauge. ^^This is the picture VileZamboni posted in the thread on Chris's board. If someone has a better picture of the dash switch/bezel and the valve showing the hose connections and the switch on the bezel it would be an appreciated addition to post it here. 1973-1975 are not likely to have return lines so you likely only have three fuel lines at the original valve. As long as you mark the valves' hoses and hook them up to the correct tanks' hardline you shouldn't have any issues. Painters tape and a sharpie... The 16 & 20 gallon saddle tanks use the exact same senders. If yours are working I'd keep them. Most 3/4 & 1 tons of that vintage likely used a transmission/axle vent on the end of a chunk of SAE J30R7 fuel line as the vapor system. Adding a three hose 1970's Corvette or F-body vapor can is an easy way to make sure the garage will not smell like raw fuel. I'm not a pushy obnoxious environmentalist. If the smell of raw fuel in the garage doesn't bother you just carry on without an evap can.
__________________
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. Last edited by hatzie; 06-05-2021 at 05:47 PM. |
|
![]() |
![]() |
![]() |
#115 |
Registered User
Join Date: Sep 2009
Location: Beaverton, OR from WA State
Posts: 1,515
|
Re: 1973-1991 Dual fuel tank systems theory of operation
When ordering/building the truck the single tank option defaulted to passenger side from 73-80, and driver's side from 81+. Hatzie has the perfect response to how the switch/valve treat the main/aux distinction. I just wanted to mention the above oddity in the two generations.
__________________
Devin 1983 GMC High Sierra 2500, 4x4, RC/LB, 400 S.B., SM-465, NP-208, Corporate 10 bolt & 9.5" 14 bolt 1996 GMC Sierra SLE 3500 DRW, 4x4, EC/LB, Vortec 454, NV-4500, BW-4401, AAM 925 & AAM 1050 1997 GMC Sierra SLT 1500 4x4, Z71/F44, EC/SB, Vortec 350 My Introduction with my '83s History New Daily, the '96 |
![]() |
![]() |
![]() |
#116 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
|
Re: 1973-1991 Dual fuel tank systems theory of operation
I had a 78 & 79 that I could swear had the tank on the LH "driver" side.
I bought em 3rd & 4th hand so the prior owners could've installed 1980's beds on em. It's also been over 30 years so I reserve the right to remember things incorrectly.
__________________
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. Last edited by hatzie; 06-06-2021 at 02:03 PM. |
![]() |
![]() |
![]() |
#117 |
Registered User
![]() Join Date: Apr 2021
Location: Phoenix, OR
Posts: 3
|
Re: 1973-1991 Dual fuel tank systems theory of operation
I have an '84 GMC K1500 that has a carburetor, mechanical fuel pump and dual tanks. Aux. tank has been disconnected (reason unknown).The PO removed all items related to EFI and emissions. It has the Pollak 6 port selector valve (which will be replaced with a new one) and Standard DS-1807 switch. All wiring and connectors are there.
Would there be any reason not to reconnect the auxiliary tank and use the new valve and switch? I also plan on installing an adjustable fuel pressure regulator with a return line back to the valve. Any help is greatly appreciated. |
![]() |
![]() |
![]() |
#118 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
|
Re: 1973-1991 Dual fuel tank systems theory of operation
84 wouldn't have Fuel Injection GM started that on the 1987 trucks.
The mechanical fuel pump will deliver fuel at the proper pressure for your carburetor from whichever tank you select. Change the switch, check for volts and ground at the plug, and then check the old valve operation before you do anything with the new valve. A fair percentage of the time the old valve will work fine. From 1981 on GM stopped using the AUX and Main designations and got right to the point LH & RH. You should make sure the LH tank is selected when the switch is set to LH and RH when RH is selected.
__________________
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. |
![]() |
![]() |
![]() |
#119 | |
Registered User
![]() Join Date: Apr 2021
Location: Phoenix, OR
Posts: 3
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Quote:
|
|
![]() |
![]() |
![]() |
#120 |
Moderator
![]() Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,951
|
Re: 1973-1991 Dual fuel tank systems theory of operation
The switch posted should run the valve if the wiring is good and the valve is in working order.
6PSI maximum pressure doesn't mean it's running that pressure all the time. It means that 6PSI is all you're going to get.
__________________
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. |
![]() |
![]() |
![]() |
#121 |
*************
![]() Join Date: Apr 2005
Location: Pensacola, FL
Posts: 17,846
|
Re: 1973-1991 Dual fuel tank systems theory of operation
By chance, does anyone have a part number for the oil pressure switch that allows the engine to start when above 10 psi? I've searched but can't find it. Thanks in advance!
__________________
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 |
![]() |
![]() |
![]() |
#122 |
Registered User
Join Date: Sep 2002
Location: Liberty, Mississippi
Posts: 671
|
Re: 1973-1991 Dual fuel tank systems theory of operation
The one on my 88 R30 w/454 was GM 25036938 (standard PS221 is the cross) this is the one for the computer, not sure what the one for the gauge is, as I’ve never changed it
|
![]() |
![]() |
![]() |
#123 | |
*************
![]() Join Date: Apr 2005
Location: Pensacola, FL
Posts: 17,846
|
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 |
|
![]() |
![]() |
![]() |
#124 |
Registered User
![]() Join Date: Oct 2013
Location: lousiville Ky
Posts: 2,649
|
Re: 1973-1991 Dual fuel tank systems theory of operation
Thanks for sharing your knowledge on this subject. 1986 K10 short bed, needs right side tank replaced, suggestion on good replacement tank, and/or key factors to look for.
Thanks, Les |
![]() |
![]() |
![]() |
#125 |
chevy truck fan
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,988
|
Re: 1973-1991 Dual fuel tank systems theory of operation
aotte1, this is the tank I purchased for my '86 2wd swb for a LS conversion. this is a 16 gal tank for shortbed purpose. you will need to get a 20 gal tank for a longbed...
link:https://www.amazon.com/Spectra-Premi...+Chevrolet+C10 hope this helps.. good luck |
![]() |
![]() |
![]() |
Bookmarks |
|
|