Swapped from dual to single tank now fuel gauge wont read

[square81]

Found my passenger side tank starting to leak. So I removed it, the switching valve and everything to do with the dual tank. I bought everything new for the driver side. Tank, sender, filler neck etc. Once everything was all hooked up I found my gauge not working. I know the ground is good and I put the pink wire back on that was there before. It only started reading right once I plugged it back into the switching valve. What does that valve have to do with this. Do I need to unplug it from the switch on the dash and switch valve then run a new "pink" wire to the gauge so I can get rid of the rest. Any input would be great. Thanks

[rich weyand]

The valve switches the gas supply line (and the gas return line if there is one), but it also electrically switches the sender unit lines to the gauge.  You should be able to take the sender unit wire from the new tank and the wire back from the gauge and both off of the valve connector and splice them together and have a working gauge.

[square81]

I'm going to give that a try. I was looking at my shop manual and just couldn't get it straight too many pinks. I'll let you know how I make out. Thanks.

[shadoe]

Hey Rich....what do you mean ......both off

You should be able to take the sender unit wire from the new tank and the wire back from the gauge and both off of the valve connector and splice them together and have a working gauge.

I also took one tank off and the switching unit, so my gauge does not work. O the tank has new sending unit plus tank is new too.

[rich weyand]

The original wiring with two tanks had 5 wires going to the solenoid valve.  One was from the switch on the dash, and one to frame ground, to power the solenoid.  The other three are the two sender wires from the tanks, and the wire back to the gauge.  When you selected a tank, the solenoid valve switched the fuel lines, but it also switched the sender wires, connecting only one of them to the gauge.  If you left the wiring connected to the solenoid valve, then you won't get a connection to the gauge from the sender on your single tank unless 1) you have the correct tank selected, and 2) the solenoid valve works.  If you identify the wire to the gauge (probably PINK), and the sender wire from the tank you are using, you can take both off the solenoid valve and simply splice them together to make sure you have that connection.

[square81]

Hey fellas here's what I did today. I did what rich said and hooked all the pink wires together. My gauge was only working intermittently very odd because it worked before. But what also happened was my switch valve was still stuck on the other tank and wouldn't switch back for whatever reason, kinda the other reason I went to single tank. After some digging around I found the problem in the dual tank harness and plug. It was full of corrosion that was my intermittent problem there. So I just found the 2 pink sender wires and followed them to a splice along the frame. Then from there I followed it up to the fuse block on the fire wall. Spliced in a new wire from there back to my new sender. After all that messing around I basically just bypassed all the original dual tank stuff and now have a working gauge. Thanks for you help guys hope this helps someone else too.

[zieg85]

It is gonna help me for sure.  I am going from a single to dual, have the factory stuff but now have a pretty good understanding on how it all works should I experience issues.  A second thanks Rich for an excellent explanation.

[rich weyand]

One thing there, zieg85, in going from single to dual.  The stock valve is a solenoid valve.  When energized, you have one tank, when relaxed, you have the other.  If the solenoid works.  The thing is, the solenoid is energized continuously whenever you are on that tank.  There is an identical solenoid valve that is motorized.  It takes two leads (not one lead plus frame ground) from the switch.  When the leads are one way, the motor moves the valve when way and then shuts off.  When you swap the polarity (with a DPDT switch), the motor moves the valve the other way and then shuts off.  Much more reliable.  The motorized valve is Pollak No. 812705 (this is the six-port valve, if you have both supply and return lines).  I got it at carparts.com: http://www.carparts.com/details/Univ/Pollak/Fuel_Tank_Selector_Switch/POL42300P.html.  Not cheap, but there's nothing more irritating than running out of gas with a full tank on hand because the solenoid failed.

[rich weyand]

BTW, that motorized valve has the same mounting holes and connections as the solenoid valve.  Looks almost identical.  No problem using it instead of the stock solenoid valve.

[zieg85]

One thing there, zieg85, in going from single to dual.  The stock valve is a solenoid valve.  When energized, you have one tank, when relaxed, you have the other.  If the solenoid works.  The thing is, the solenoid is energized continuously whenever you are on that tank.  There is an identical solenoid valve that is motorized.  It takes two leads (not one lead plus frame ground) from the switch.  When the leads are one way, the motor moves the valve when way and then shuts off.  When you swap the polarity (with a DPDT switch), the motor moves the valve the other way and then shuts off.  Much more reliable.  The motorized valve is Pollak No. 812705 (this is the six-port valve, if you have both supply and return lines).  I got it at carparts.com: http://www.carparts.com/details/Univ/Pollak/Fuel_Tank_Selector_Switch/POL42300P.html.  Not cheap, but there's nothing more irritating than running out of gas with a full tank on hand because the solenoid failed.

Awesome, thanks I will be saving this thread in my favorites.  Actually my uncle cobbled up a second tank which was rusted out when I got the truck so it kinda has dual tanks but I have no idea if what he installed still works.  My new bed has provisions for dual tanks I snatched all the wiring that was associated with the dual tank setup for under the dash and beyond the firewall.  Cost will be no issue, I want to do it right.

[rich weyand]

Well, you need an extra wire from under the dash for the motorized valve.  The valve includes the connector and the reversing switch for in the dash.  I mounted my switch in the existing round hole in the dash under the radio, back toward the back lip under the dash.

The tank straps come from the factory riveted to the L-brackets that go on the frame.  When I replaced the straps, I used sidewalk bolts to attach them to the L-brackets, because sidewalk bolts are so flat on the head end that I could run one layer of anti-squeak around them and then one layer over them, and I didn't have to worry about the bolt heads rubbing on the tank.  Here's the sidewalk bolts I used: http://www.mcmaster.com/#90015a414/=o837or, and I used them with nylon-insert locking nuts: http://www.mcmaster.com/#91831a029/=o8380l.

If you don't know about McMaster-Carr, you're in for a treat.  We used to get their catalog where I worked, and it was about 3000 pages of hardware and supplies.  When I was in the Chicago burbs, if I ordered before 11 AM, it would come in on the afternoon truck.

I also used the spare gauge position on the dash to mount a second gas gauge.  If you have a tach, that's where a small gas gauge goes.  I don't have a tach, so I got one of the little gas gauges as NOS and installed it there.  Now each tank has its own gauge, and I don't have to switch tanks to see both levels.  Note the two gas gauges in this pic: http://users.rcn.com/weyand/smalls/dsc03135small.jpg

Anything else on this project, just ask: weyand AT rcn DOT com.  BTDT, three years ago, and I love how it worked out.

[square81]

That's a nice idea with the second gauge, looks very factory.

[rich weyand]

That's a nice idea with the second gauge, looks very factory.

Yeah, and it fills the stupid blank position in the dash, which was always kinda klugey.

[shadoe]

Since I took out the solenoid valve and then splice like you said..   "  If you identify the wire to the gauge (probably PINK), and the sender wire from the tank you are using, you can take both off the solenoid valve and simply splice them together to make sure you have that connection.".....does it matter about the dash switch still being connected?

[rich weyand]

The dash switch just runs the solenoid valve.  If the valve is disconnected from the fuel lines and sender wires, the switch will have no effect.