The 1947 - Present Chevrolet & GMC Truck Message Board Network







Register or Log In To remove these advertisements.

Go Back   The 1947 - Present Chevrolet & GMC Truck Message Board Network > 47 - Current classic GM Trucks > The 1973 - 1987 Chevrolet & GMC Squarebody Pickups Message Board

Web 67-72chevytrucks.com


Reply
 
Thread Tools Display Modes
Old 06-14-2020, 02:23 PM   #101
rodstored-72
chevy truck fan
 
rodstored-72's Avatar
 
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,657
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.
rodstored-72 is offline   Reply With Quote
Old 09-30-2020, 03:06 PM   #102
Mixup
Registered User
 
Join Date: Jan 2002
Location: Henderson, NV
Posts: 357
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.
Mixup is offline   Reply With Quote
Old 10-02-2020, 09:51 AM   #103
aggie91
I'm just glad to be here!
 
aggie91's Avatar
 
Join Date: Jan 2008
Location: Longview, TX
Posts: 4,603
Re: 1973-1991 Dual fuel tank systems theory of operation

Quote:
Originally Posted by Mixup View Post
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?
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
aggie91 is offline   Reply With Quote
Old 04-08-2021, 06:10 PM   #104
SunSoaked
Registered User
 
SunSoaked's Avatar
 
Join Date: Dec 2011
Location: Yuma Arizona
Posts: 1,400
Re: 1973-1991 Dual fuel tank systems theory of operation

Quote:
Originally Posted by rodstored-72 View Post
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.
I have a similar question. On my 85 with factory dual tanks, am I splicing into the power wires to the senders to run the fuel pumps? Where does the "relay" come into play mentioned in earlier posts? Was that just a safety feature for the factory TBI systems from 87 up?
SunSoaked is offline   Reply With Quote
Old 04-09-2021, 09:33 AM   #105
hatzie
Moderator

 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,309
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...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 04-09-2021 at 09:59 AM.
hatzie is offline   Reply With Quote
Old 04-13-2021, 07:25 PM   #106
rodstored-72
chevy truck fan
 
rodstored-72's Avatar
 
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,657
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!!!
rodstored-72 is offline   Reply With Quote
Old 04-13-2021, 07:44 PM   #107
SunSoaked
Registered User
 
SunSoaked's Avatar
 
Join Date: Dec 2011
Location: Yuma Arizona
Posts: 1,400
Re: 1973-1991 Dual fuel tank systems theory of operation

Main is driver side (from the seated POV).
SunSoaked is offline   Reply With Quote
Old 04-13-2021, 07:48 PM   #108
hatzie
Moderator

 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,309
Re: 1973-1991 Dual fuel tank systems theory of operation

Quote:
Originally Posted by rodstored-72 View Post
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!!!
1981-1991 tank switches are marked RH & LH. The tank you use as your "main" tank is up to you.
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...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 04-13-2021 at 08:29 PM.
hatzie is offline   Reply With Quote
Old 04-14-2021, 10:53 AM   #109
rodstored-72
chevy truck fan
 
rodstored-72's Avatar
 
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,657
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....
rodstored-72 is offline   Reply With Quote
Old 04-18-2021, 02:22 PM   #110
rodstored-72
chevy truck fan
 
rodstored-72's Avatar
 
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,657
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!
rodstored-72 is offline   Reply With Quote
Old 04-18-2021, 03:45 PM   #111
hatzie
Moderator

 
hatzie's Avatar
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,309
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...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.
hatzie is offline   Reply With Quote
Old 04-19-2021, 11:34 AM   #112
rodstored-72
chevy truck fan
 
rodstored-72's Avatar
 
Join Date: Mar 2005
Location: Gilbert, arizona 85298
Posts: 1,657
Re: 1973-1991 Dual fuel tank systems theory of operation

Quote:
Originally Posted by hatzie View Post
Sounds right.
thanks!!
rodstored-72 is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 10:06 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Copyright 1997-2020 67-72chevytrucks.com