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Old 11-04-2018, 06:04 PM   #1
sweetk30
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tank switch in dash for tbi trucks ?

does the in-dash switch for the tank switch left or right have full amperage going threw it for the fuel pump power ?

i am not using the oem system . this was extra parts i had and making a transfer switch setup to fill the extra dash hole .

i want to send power to the pump threw the switch only .

i pined out the switch so i know what pins i can use for this .

just need to know if i can use just the switch for free flow transfer of fuel to other tank with a stock tbi pump/sender in the tanks . or do i need a relay for this ?

thanks for any help guys .
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Old 11-04-2018, 11:59 PM   #2
hatzie
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Re: tank switch in dash for tbi trucks ?

The stock NL2 switch carried the full fuel pump amperage.
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1986 M1008 CUCV
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Old 11-05-2018, 11:41 AM   #3
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Re: tank switch in dash for tbi trucks ?

so are you saying i have the nl2 switch ?
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Old 11-05-2018, 02:21 PM   #4
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Re: tank switch in dash for tbi trucks ?

If your truck came with dual fuel tanks RPO NL2 will be on your SPID in the glovebox and on the build sheet stuffed into the seat springs.

There were actually three different switches used on the NL2 system.
1973-1980 will work out of the box. It's a DPDT switch with one terminal removed to key the connector.
1981-1986 will not work. It's a momentary Polarity Reversing switch that springs back to a centre off position. It's marked DEPRESS FULLY.
1987-1991 will work with some head scratching. This is a continuous Polarity Reversing switch with two ON positions and no centre OFF.

Either non-momentary switch will carry the amperage necessary to power a fuel pump.
My first choice would be the 73-80 switch.
If you have the AC Delco D7089C switch you have the polarity reversing NL2 switch that ran the TBI fuel pumps.
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1959 M35A2 LDT465-1D
1967 Dodge W200 B383, NP420/NP201
1969 Dodge Polara 500 B383, A833
1972 Ford F250 FE390, NP435/NP205
1976 Chevy K20, 6.5L, NV4500/NP208
1986 M1008 CUCV
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; 11-05-2018 at 02:37 PM.
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Old 11-05-2018, 04:58 PM   #5
sweetk30
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Re: tank switch in dash for tbi trucks ?

my switch was 87 tbi 2 tank system .
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Old 11-10-2018, 04:25 AM   #6
cerial
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Re: tank switch in dash for tbi trucks ?

I just did this to my 87 installing a inline frame mounted Walboro pump retaining the factory oil pressure wiring and shutoff.


I pulled the switch then disconnected the harness at the back and stuffed a test light into the terminal turned the key on and the pump power will light up for 2 seconds when you get the correct one. Should also light up if you crank the truck 3 to 5 times showing you that the oil pressure circuit is working properly.

I cut the wire a bit back from the connection soldering the old to new wire and then taped up everything before popping the old switch in place so there would not be a hole in the dash. Then I ran the new 10 gauge wire to a relay near the pump to lessen strain on the factory wiring.

Your tank sending unit wire is the pink one located down by the switcher. The pink and white goes to a tank and the pink and black goes to the other tank. But the solid pink one is the one that goes to your gauge and is what you want to hook up to your new tanks sending unit.

Here is a wiring diagram for the 2 tank switch setup.

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Last edited by cerial; 11-10-2018 at 04:35 AM.
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Old 11-10-2018, 11:45 AM   #7
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Re: tank switch in dash for tbi trucks ?

i am just using the SWITCH ONLY from the 87 tbi 2 tank setup .

the one member said it will hold the full power if its the XXX model switch . . . i then asked if that is in fact the one i have ? as i dont know these systems .

i just want to use it for 2 reasons . plug the hole in the dash . and send power to the pass side tank to pump to the driver side tank when needed .

thanks for all the info guys .
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Old 11-10-2018, 01:47 PM   #8
hatzie
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Re: tank switch in dash for tbi trucks ?

If you only use the 87-91 Polarity Reversing dash switch to control the HOT to the fuel pump it'll work just fine.

Look at post #2 of the dual tanks theory of operation thread for an explanation of what that switch does...
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1959 M35A2 LDT465-1D
1967 Dodge W200 B383, NP420/NP201
1969 Dodge Polara 500 B383, A833
1972 Ford F250 FE390, NP435/NP205
1976 Chevy K20, 6.5L, NV4500/NP208
1986 M1008 CUCV
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.
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Old 11-10-2018, 03:16 PM   #9
sweetk30
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Re: tank switch in dash for tbi trucks ?

all i planned on doing was power in switch and out to pump was all . the rest of the system i have a seperate autometer fuel level gauge and a big red light to turn on when i am pumping so i dont forget and over fill the main tank .
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Old 11-12-2018, 03:02 PM   #10
sweetk30
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Re: tank switch in dash for tbi trucks ?

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Last edited by sweetk30; 11-12-2018 at 04:05 PM.
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Old 11-12-2018, 08:32 PM   #11
hatzie
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Re: tank switch in dash for tbi trucks ?

I'd probably move fuel when the primary tank is 1/4-3/8 and not fill the primary much over 3/4 when schlepping fuel tank to tank.
It's mildly dangerous so you have to be on top of your game when you do it. Not nodding off at 01:00 on a rural section of interstate.
I'd also consider putting a power lockout switch somewhere hidden to keep the kids or wife or girlfriend or ... from activating the fuel transfer.
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1959 M35A2 LDT465-1D
1967 Dodge W200 B383, NP420/NP201
1969 Dodge Polara 500 B383, A833
1972 Ford F250 FE390, NP435/NP205
1976 Chevy K20, 6.5L, NV4500/NP208
1986 M1008 CUCV
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.
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Old 11-12-2018, 09:45 PM   #12
sweetk30
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Re: tank switch in dash for tbi trucks ?

wife/ kids / girl friend / dog . . . i am so far ahead with non of them . . . the right one just has yet to find me and ask me out on a date . but yes a master power switch before this switch would be good . and my big red light also will help .
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