Author Topic: ‘79 K10 fuel switching valve retrofit (wiring)  (Read 4716 times)

Offline bake315

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‘79 K10 fuel switching valve retrofit (wiring)
« on: May 09, 2020, 09:37:51 PM »
Hey guys,

So I’m most of the way through restoring the fuel system on “Oscar” and have completed the plumbing in of the 6-port replacement valve.  Now I just need to get the little bit of wiring sorted.  At this point, the left side (auxiliary) tank sender has been working fine, and the light blue wire running up to the switch seems in good shape.  What I’m not all that certain of is the wiring for the primary sender.  It was severed right at the connection on top of the sending unit. 

I have three wires running over to the valve and primary tank:

A pink(ish) wire that is so badly faded that, based on its end, I’m fairly certain that it’s the sending unit wire

A green wire

A pinkish, almost white, almost tan wire, also badly faded in spots, with the same rubber connector that the connection on top of the sender uses.  However, after the connector, the wire was cut, and effectively goes nowhere.

The Chevy wiring diagram is sort of vague (to me) as to where each of these terminates.  I feel pretty confident about the sending unit wire, but am very unsure about the other two.  The first photo are the three wires in question.  The second photo is the pigtail from the replacement valve, where I have labeled each wire coming off of it.  I need to know which of these to use in completing the circuits.

Thanks much,

bake315
« Last Edit: May 10, 2020, 09:20:59 PM by bake315 »
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Offline VileZambonie

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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #2 on: May 10, 2020, 05:27:49 PM »
Hi Vile,

Thanks for this.

So I have worked out that the green lead hanging under the truck would be able to drive the valve motor, but in only one direction. Basically because it is motorized, and not a solenoid switch, then I actually can’t use the Pollak valve - or at least not without the additional NL2 sub harness, am I reading that correctly?

If that’s the case, then - short of coughing up yet even more coin for a “unicorn” NOS 6-port, then I am essentially stuck re-capping the return lines (one of the PO’s had done the same thing) and using the Standard 3-port switching valve, I guess?
« Last Edit: May 10, 2020, 11:25:17 PM by bake315 »
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Offline Geezer77GMC

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #3 on: May 11, 2020, 10:16:23 AM »
Try this link, also look at the instruction form for the product on the page.
https://www.rockauto.com/en/moreinfo.php?pk=660983&cc=1030217&jsn=452
Looks fairly straight forward. Also check Digikey for rocker switch.
« Last Edit: May 11, 2020, 10:33:43 AM by Geezer77GMC »

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #4 on: May 12, 2020, 07:46:22 AM »
Try this link, also look at the instruction form for the product on the page.
https://www.rockauto.com/en/moreinfo.php?pk=660983&cc=1030217&jsn=452
Looks fairly straight forward. Also check Digikey for rocker switch.
Yes, I have this manual.  RockAuto is where I bought the valve.  Thanks just the same.

I’ll work this out on my own, I guess.
« Last Edit: May 12, 2020, 09:56:28 AM by bd »
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Online bd

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #5 on: May 13, 2020, 03:10:44 AM »
Original 1-Wire Valve:
Referencing the relevant information in Hatzie's thread previously linked, the '79 factory tank selector switch on the dash serves two functions.  1) It directly selects to which fuel sender the dash gauge is connected (pink, blue, & yellow wires below). 2) It energizes the tank selector valve in the auxiliary tank position and de-energizes the valve in the default, primary tank position (green wire).




Service 5-Wire Valve:
The replacement 5-wire tank selector valve (image below) is motorized and houses two slave operated SPDT switches.  The valve assembly contains a rack that motors left and right to actuate the two slave operated switches in conjunction with the fuel valve.  The SPDT switches change state each time the motorized rack reaches the extremes of its travel.  The common pole of one SPDT switch connects directly to the dash gauge through terminal B.  The outer two poles of that same switch independently connect to the left and right fuel tank senders such that as the valve motors left and right in concert with the position of the dash switch, the gauge is switched between the left and right tanks, terminals C and A, respectively. 



The common pole of the second slave operated SPDT switch connects to the dash-mounted (DPDT) tank selector switch through terminal E.  The outer two poles of that second SPDT switch independently connect through polarity opposed diodes to one pole of the tank selector valve motor.  The opposite pole of the selector valve motor connects directly to the dash switch through terminal D.



The tank selector valve momentarily energizes and motors between the left and right tank positions by reversing the direction of current flow through the valve motor.  The dash-mounted selector switch serves the sole purpose of reversing electrical polarity on the two wires that energize the valve motor.

The 5-wire selector valve will replace the original 1-wire valve by performing minor modifications to the wiring. 



The red and tan labeled wires connect to one pair of either end terminals of a DPDT switch.  The four end (corner) terminals of the switch should be jumpered in an X configuration.  The two center terminals of the switch connect to ignition power and ground.  This configuration will reverse polarity on the two wires running to the selector valve whenever the switch is flipped.



If you want to maintain an original look, consider using an AC Delco D7089C selector switch from the TBI equipped trucks (imaged below).  The switch is internally jumpered in an X configuration from the factory.  It should fit the rectangular opening in the dash (assuming one is already there) and simply snaps into the factory cutout.  Finding a single molded connector that mates with the square terminal configuration of the switch may be a challenge, but the switch is pre-configured for your purpose, using just four wires: ignition, ground, and the two wires routed to the selector valve as previously described.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #6 on: May 13, 2020, 10:06:38 PM »
Tremendous write-up!  I can't tell you how much I appreciate it!

bake315
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Online bd

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #7 on: May 14, 2020, 10:51:54 AM »
You are quite welcome for the assistance.  Yet, thanks should go to Hatzie.  All that I did was to reference his thread.   8)
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #8 on: May 16, 2020, 01:25:43 PM »
You are quite welcome for the assistance.  Yet, thanks should go to Hatzie.  All that I did was to reference his thread.   8)

Yes, much thanks to Hatzie for providing his images, plus all those other diagrams.  The ‘79 truck set have become almost a Bible
 of sorts for me.
« Last Edit: May 16, 2020, 02:33:33 PM by bake315 »
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #9 on: May 16, 2020, 05:34:30 PM »
Hi again,

Okay, so I'm just about ready to start preparing the sender and gauge circuits between the new switching valve, and the new D7089C selector switch, and my question is, should I:

  • Run new conductors from valve to gauge, and valve to switch
or
  • Try and use the existing conductors, re-purposed?

I've been going back and forth on this; part of me wants to run new wiring to ensure I have complete connection integrity (in case the originals have hidden damage).  On the other hand, I'd rather not add wire unnecessarily, if what is present (with all its bulkhead pass-throughs) will do the job.

What would y'all do?

Thanks as always,
bake315
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Online bd

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #10 on: May 16, 2020, 06:32:21 PM »
If the original wiring appears to be in good physical condition and there is excellent continuity, I would repurpose the existing wires.  You will still need to route a new ground wire to the switch.  Solder the terminal crimps to the wires using 60/40 rosin core.  If you decide to string new wire, I recommend GXL or SXL.  With new wire you could eliminate the pigtail off the 6-way selector valve connector and terminate the new wires with new Weatherpack terminals for direct insertion into the connector doing away with external butt splices that might corrode.  Otherwise, shrink-seal all exposed splices using marine grade heat shrink.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #11 on: May 16, 2020, 09:54:04 PM »
If the original wiring appears to be in good physical condition and there is excellent continuity, I would repurpose the existing wires.  You will still need to route a new ground wire to the switch.  Solder the terminal crimps to the wires using 60/40 rosin core.  If you decide to string new wire, I recommend GXL or SXL.  With new wire you could eliminate the pigtail off the 6-way selector valve connector and terminate the new wires with new Weatherpack terminals for direct insertion into the connector doing away with external butt splices that might corrode.  Otherwise, shrink-seal all exposed splices using marine grade heat shrink.

After giving it a little bit of thought, I think I am going to run new .8 GXL conductors; one of the existing ones didn't really seem to measure up continuity wise, and I'd rather not have to cross this real estate a second time.  Also, really like the Weatherpack approach.  Found the six port Weatherpack plug online that will eliminate the pigtail, and make it go back together just right.  I will still have two splice points - at the sending unit connections - but they'll be done with marine-grade shrinkable butt connectors, as per usual.

10-4 on the ground wire at the switch.

Thanks again!
bake315
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #12 on: May 17, 2020, 07:18:03 PM »
Today I pulled the entire fuel supply wiring harness from the bulkhead connector on back.  As I suspected, some damage was found, on the auxiliary tank conductor, less than three inches from the bulkhead connector.  Ruptured on one side, and nicked almost to the strands on the other side.

• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #13 on: May 23, 2020, 05:17:47 PM »
Well, so much for my holiday weekend plans.  Ordered wire from Wirebarn, and a switch from RockAuto.  Both shipped USPS. Both arrived in Austin on the same truck.  Both arrived in Elgin on the same truck.  According to the USPS website, both went out for delivery at 7:35 this morning.

The switch arrived.  The wire did not.  >:( Really, USPS?

Would love to fully (and colorfully) articulate my present mood, but it might earn me being banned for life.  ;D

Being that this is a holiday weekend, I have to wait until Tuesday to get my wire.

When they managed to lose my property tax check over 10 years ago, I swore I would never again willingly choose them as a means of delivery. 

This is why.  Grrrrr.  I’m going to write the Elgin postmaster a letter, and give him a piece of my mind.  Trust me - it’ll be a doozy!
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”

Offline bake315

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Re: ‘79 K10 fuel switching valve retrofit (wiring)
« Reply #14 on: June 01, 2020, 02:48:07 PM »
Howdy folks.

Okay, so I finally received the wire that I’d ordered, and so set about the task of creating my new fuel switching valve wiring harness.  The first picture is the harness consisting of three wires; switching circuits for each side, plus the fuel gauge circuit, now controlled at the valve assembly.

The second picture is the same harness, wrapped in the same type of non-adhesive vinyl tape as what came from the factory.  This stuff was surprisingly easy to work with.  Running the new harness was a breeze, as was the removal of the old one.

The third picture shows the reverse side of the newer model switch, indicating proper circuit position.

My next post will illustrate the final terminations on each end along with the final installation of the switch in the dash.
• '73 Cheyenne Super C20 454/400 http://forum.73-87chevytrucks.com/smforum/index.php?topic=7672.0
• ’79 Scottsdale K10 350/NP208/SM465 “Oscar” http://forum.73-87chevytrucks.com/smforum/index.php?topic=37885.0
• ’87 Custom Deluxe R30 350/400 “Felix”