A request for assistance with Fuel transfer valve, switch, and fuel gauge

WP29P4A

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I don't like doing a project like you are doing and using the faith based approach, where I follow the instructions and put everything together, then test it and it doesn't work. Then I have to take it all apart and try to figure out what went wrong, or what brand new part is defective, or what part of the instructions are incomplete. I use the test leads to "mock up" the system so I can test it BEFORE I finish installing the system.

When I did the gauge installation pictured above I tested every individual item as I moved forward.
 
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WP29P4A

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This is a tool for locating wires and it has a continuity function also. The little box in the back ground gets connected to the wires and produces a "tone" on the wire. The wand in the foreground is for locating the tone. When you pass it near the correct wire it detects the tone, when you touch the insulation on the correct wire it gets louder, when you actually touch the bare end of the wire it gets real loud, confirming the correct wire. They cost between $100 and $200

When your frustration level is ramping up from using the force to unsuccessfully to track down wires, this tool can get you from point A to point B without following the map to get there. When I had to track down the tach wire coming out of the ECM with a white wire and changing to orange with a white stripe before coming out of the wiring loom behind the dash, with no diagram or color code, I used the wire locator as shown above. Found the wire in minutes and moved forward with the repair.
 

Donald Bartlett

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Agreed gentlemen.

So at this point here is what I have done now.

I have placed an independent ground wire from the back of the gas gauge to a known good ground behind the cluster.

I know that I'm getting good power to the gauge from the wire that I used which was the pink one (keyed hot).

I took off both ground wires from the gas tank sending unit to the frame, and use a die grinder to clean the frame to bare metal and rebolted them down. I also ran a brand new wire from the sending unit terminal on the gas gauge down to the 213 pigtail.

I verified each of the wires on the pigtail are going to the correct locations. Although I have not replaced the wires from each tank to the pigtail they were working previously.

Now, when I turn the key on, the needle moves a little bit but essentially sits at the empty mark.

When I switch the DPDT from one position to another, the needle moves a little bit (I believe indicating a tank change), and I believe I hear the small motor in the fuel valve operating.

I am still getting an empty reading on each tank though. I know for a fact on my driver side tank there is 15 gallons in there and it should be reading something.

I have to admit I'm completely stymied.

- I know the gauge has a good ground.

- I know that the grounds from the sending units to the frame are clean and fresh.

- I know that I'm getting 12 volts to the gauge. I know that I'm getting voltage down to the 213 pigtail.

- Brand new sending units.

I have pretty much replaced each wire to the gauge with brand new wiring in the hopes of eliminating any bad wiring, ground issues or the like with the factory wires.

Correct me please if I am incorrect here: I should have each of the sending unit wires into the valve in pins A & C, and the wire to the gauge comes from pin B. The valve should allow each sending unit wires to "report" to the gauge through the B pin location the gauge, right?

Ugh.

Lol.
 

Donald Bartlett

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I don't like doing a project like you are doing and using the faith based approach, where I follow the instructions and put everything together, then test it and it doesn't work. Then I have to take it all apart and try to figure out what went wrong, or what brand new part is defective, or what part of the instructions are incomplete. I use the test leads to "mock up" the system so I can test it BEFORE I finish installing the system.

When I did the gauge installation pictured above I tested every individual item as I moved forward.
....... And that very well may be where I blew it. I did not verify that each of the sending units worked. I suppose this is where an ounce of prevention comes in. I have course, figured the sending units work properly since they were brand new. Yes, I suppose I should know better than that LOL

Another thing is that for all I know the electric fuel valve may not be functioning properly.

I am kind of at this point where I'm so pissed off and frustrated by it it's like I need to walk away for a month LOL.

Unfortunately, I can't do that cuz I need my truck LOL.
 

Donald Bartlett

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Okay, little bit of an update: I went ahead and lifted the truck back up and lowered the passenger side tank.

I double checked all of the wiring grounds and everything. I had power down to the 213 pigtail, at the right pin and I had power to the sender. I also had power on the return wire back up to the gauge.

Just for the hell of it, I took one of my old sending units and hooked it up and lo and behold the gas gauge worked. I could move the lever and it would show the according reading on the gauge.

I went ahead and took the new sending unit out of the new tank hooked it up to the wiring, and nothing..

Hooked up the old sending unit one more time out of the tank with just the plug on the top and a ground wire to frame and again it worked just fine.

I am starting to believe that I may have just gotten too bad sending units, or possibly ones that have the wrong ohms level possibly?

I had ordered them from classic Chevy who is usually really good about getting you the right stuff for the right years of vehicle. I am not in any means trying to blame them I'm actually trying to support that I was very certain I had the correct sending units. Maybe I do and they are just bad.
 

SirRobyn0

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Okay, little bit of an update: I went ahead and lifted the truck back up and lowered the passenger side tank.

I double checked all of the wiring grounds and everything. I had power down to the 213 pigtail, at the right pin and I had power to the sender. I also had power on the return wire back up to the gauge.

Just for the hell of it, I took one of my old sending units and hooked it up and lo and behold the gas gauge worked. I could move the lever and it would show the according reading on the gauge.

I went ahead and took the new sending unit out of the new tank hooked it up to the wiring, and nothing..

Hooked up the old sending unit one more time out of the tank with just the plug on the top and a ground wire to frame and again it worked just fine.

I am starting to believe that I may have just gotten too bad sending units, or possibly ones that have the wrong ohms level possibly?

I had ordered them from classic Chevy who is usually really good about getting you the right stuff for the right years of vehicle. I am not in any means trying to blame them I'm actually trying to support that I was very certain I had the correct sending units. Maybe I do and they are just bad.
At this point with all you have done I am not surprised one bit that it turns out to be defective parts. You can order those sending units for any auto parts store to by the way. At the shop we have had very good luck with the spectra sending units that Oriellys sells.
 

hip2bsquare

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i am thinking that it might be the sending unit(s) as well?? and the thought of new parts not working from the get-go is a strong possibility... i just went through a new fuel pump & dash switch due to the new previous part(s) not working. amazon---you have to love it....& you have to hate it. the bad new parts were able to be kept & 2nd new parts were shipped the next day. maybe the sending units are not reading the correct ohms??
 

WP29P4A

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I think you learned some valuable trouble shooting lessons. Keeping the old parts until the new stuff is in and working, is a really good idea. Using the old parts to compare with new parts function is helpful too. Major kudos on your diagrams and logic by the way. It's sad that it's gotten to the point that we have to test our new parts to save the hassle of installing defective/incorrect parts and then having zero confidence that the 2nd replacement part will work.

Having BOTH new senders not working would have messed with my trouble shooting logic/path and would have definitely slowed me down a lot until I got pissed and desperate enough to try the old sender like you did. I would put a meter on the old sender and measure the empty resistance and the full resistance, write it down and test the new ones when they arrive. I sure after what you went through you already thought of it.
 

Soundmound

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Spectra senders worked well for me. Now, I did bench test them before installing them in the new tanks. Mostly because I am lazy and don't like doing things twice. I actually have used either Spectra or Delco parts almost exclusively so far and no complaints yet.
 

SirRobyn0

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@Soundmound I'm sure you have seen some of my parts posts, but ya it's really terrible. Some brands are just junk. Wiper motors for our trucks are a nightmare. ACDelco still lists a PN for our trucks but they have been out of stock for like 3 years, I think they are discontinued at this point and they haven't updated. So a few years back mine goes out. The only thing available is Cardone reman, or a repackaged store brand (NAPA) made by, you guessed it Cardone, grrr. So got one. Actually I got three. The last one failed on my in a terrible rain storm coming over tiger mountain with a loaded trailer. Then I discovered WIA, a Korean manufacture making new wiper motors for our rigs, I got one and it was a dead ringer for my OEM ACDelco unit and has worked fine. I subsequently installed a few WIA parts at the shop and it has gone well.

This is one of the reasons I never recommend purchasing parts online. Back when Rockauto was young I had to return a couple of parts and I got pay the initial shipping and the return shipping which ruined any savings on the stuff I did keep. I will admit to buying some automotive stuff from Amazon, but with prime, shipping is free. What I do is only order stuff that I know I won't return. For example I just ordered belts for my truck on Amazon, I did it because I already know the part #s, and I wanted Dayco brand. No one locally carries Dayco except one wholesale place and they have to come from another warehouse which means they add shipping charges, which make Amazon cheaper. So that's my method anyway.
 

75gmck25

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I put new sending units in both tanks of my ‘75 GMC K25 a few years ago and I got them from Autozone. Closest store did not stock them so I had to drive about 20 miles to a different store. I have the original 6 port solenoid with only a single power terminal, so my wiring is basically stock.

The older tanks have no baffles, so there is fuel sloshing back and forth and the gauge reading changes as the truck moves. On a quick uphill run it is best to have the tank over 1/4 full so the sending unit pickup stays fully immersed in fuel.
 

Nuckollsr

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I got rid of that monkey-motion transfer valve. I plumbed both pumps to the carburetor via check valves. Either pump will run the engine. Plumbed return line to right tank only. Use simple two-pole, two-position switch to select pump and associated sender. Sticker on fuel gage says 'use right tank up first'. This means that switching to left tank will not overflow the right tank with return fuel. When left tank is empty, go back to right tank an use return 'residual' fuel. Stone simple.
 

75gmck25

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On the older carbureted trucks you only have a single mechanical fuel pump. If the tanks use a 3 port sending unit (supply, return, vent) with a return line you need to switch both return and fuel supply lines, so it requires the 6 port valve.
 

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