Dual tank fuel gauge makes no sense.

mtbadbob

Full Access Member
Joined
May 9, 2021
Posts
286
Reaction score
265
Location
Montana
First Name
Bob
Truck Year
1987
Truck Model
V20
Engine Size
350
My only problem is that when my right tank gets below 1/4 full, my truck will periodically die, like the pump loses pressure or prime. It'll immediately start back up, but it's kind of dangerous & annoying as I'm usually slowing down to turn or stop when it does this. I guess I may have to pull my tank and investigate why, or replace the new pump I had just installed this past summer. :mad:
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
4,485
Reaction score
5,175
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
My truck does not have the rocker switch, and my fuel gauge reads correctly on each tank. I was merely informing JM of KY on the status of my '87 TBI set-up as I thought he suggested that the newer switches were the rocker-type, which mine isn't. My switch is the correct one that stays depressed on the selected tank. As you know, the switches will not interchange with the different factory harness plugs as there is an odd pin on the back of the switch to prevent that from happening. If you look them up on NapaOnline, you can view both types of switches & see the difference in the switch pins/terminals.
Right. Sorry about that, I was apparently confused on who was having the issue needing help. I do apologize for that.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
4,485
Reaction score
5,175
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
My only problem is that when my right tank gets below 1/4 full, my truck will periodically die, like the pump loses pressure or prime. It'll immediately start back up, but it's kind of dangerous & annoying as I'm usually slowing down to turn or stop when it does this. I guess I may have to pull my tank and investigate why, or replace the new pump I had just installed this past summer. :mad:
I can sort of relate. My truck is carbureted so I'm drawing from the tank. It was originally a single tank truck, when I bought it I was not happy with number of miles I could travel before needing to fill up, when I was loaded or more over if I was towing my trailer. So installed a second saddle tank. Now I'm not the kind of guy that likes to run his gas tank to low, I typically like to leave a 1/4 tank buffer, but I have a method to get the most miles out of the two tanks. Fill them both, run the left one until it's empty, as in hammered on E then run the right down to a 1/4 and refill. Well there have been a few times when I've been less than mindful how long I've driven on the left tank very low and ran it out. I've got a good strong fuel pump it didn't take to much cranking to get it going again, but yea I understand the feeling you are describing.
 

JM in KY

Junior Member
Joined
Oct 27, 2022
Posts
26
Reaction score
40
Location
Lexington, KY
First Name
John
Truck Year
1987
Truck Model
Sierra Classic
Engine Size
350
Just to close the loop here:

To review, my truck would show me the fuel level in the left tank only, regardless of which tank was selected. The switch inside the cab correctly switched the fuel pumps, which I verified while the truck was running and by accessing the testing wire in the relay at the top of the firewall.

I played around with this for a couple weeks. Didn’t want to accept that the new fuel selector valve I put in would be the problem.

Well, turns out the brand new AC Delco selector valve WAS the problem. I unplugged the weatherpak connection and just jumped the wires that lead to the gauge. I could make it go to empty or full on either circuit leading to the gauge. This told me the wires leading to the gauge should be able to correctly display the fuel level for either tank.

So, I put in a second brand new fuel selector valve and now everything works fine.
 

SirRobyn0

Full Access Member
Joined
Dec 6, 2019
Posts
4,485
Reaction score
5,175
Location
In the woods in Western Washington
First Name
Rob
Truck Year
1984
Truck Model
C20
Engine Size
305
Just to close the loop here:

To review, my truck would show me the fuel level in the left tank only, regardless of which tank was selected. The switch inside the cab correctly switched the fuel pumps, which I verified while the truck was running and by accessing the testing wire in the relay at the top of the firewall.

I played around with this for a couple weeks. Didn’t want to accept that the new fuel selector valve I put in would be the problem.

Well, turns out the brand new AC Delco selector valve WAS the problem. I unplugged the weatherpak connection and just jumped the wires that lead to the gauge. I could make it go to empty or full on either circuit leading to the gauge. This told me the wires leading to the gauge should be able to correctly display the fuel level for either tank.

So, I put in a second brand new fuel selector valve and now everything works fine.
I get it, sometimes it's hard to think a new part is bad, and from companies generally trusted like ACDelco, it's harder, but still happens. Glad you have a functional gauge again!
 

Dleslie212

Full Access Member
Joined
Sep 2, 2019
Posts
58
Reaction score
15
Location
Phoenix
First Name
Dustin
Truck Year
1977
Truck Model
K10
Engine Size
5.7L 350

gogo14910

Junior Member
Joined
Dec 19, 2021
Posts
22
Reaction score
28
Location
Texas
First Name
Joe
Truck Year
1987
Truck Model
R10
Engine Size
350 SBC
This diagram helped me connect the correct fuel sending unit when I deleted the selector valve and passenger tank. It’s in my thread, “help! tank delete”.
 

Attachments

  • 8A77EEEC-2D99-459C-A36E-5D5FFD64A852.png
    8A77EEEC-2D99-459C-A36E-5D5FFD64A852.png
    432.7 KB · Views: 15

Forum statistics

Threads
37,489
Posts
802,664
Members
27,491
Latest member
grimm106
Top