Author Topic: Another Fuel Gauge Question  (Read 1927 times)

Offline Harmon

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Another Fuel Gauge Question
« on: June 24, 2019, 09:38:16 AM »
86 Chevrolet C10

10 years ago I...
    - Took out passenger fuel tank because it was rusted.
    - Replaced fuel sending unit in driver fuel tank.
    - I think the gauge worked for a few days? 
    - Checked ground, and also replaced the fuel gauge in the instrument cluster.
    - I know on the driver side of the truck there is a wire that was cut, that I connected that looks Pink I think (im color blind) and I reconnected it.

Life happens and now I am getting everything right on it, and I am back to tackling this issue. 
      The fuel gauge when full says around half a tank.  Im leaning toward replacing the fuel tank sending unit again.

Ideas?
 

Offline VileZambonie

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Re: Another Fuel Gauge Question
« Reply #1 on: June 24, 2019, 11:49:12 AM »
Pull the wire off of the sending unit. Key on, observe the gauge. It should go past full. Ground the wire to a good ground and the gauge should read empty.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

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

Offline Harmon

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Re: Another Fuel Gauge Question
« Reply #2 on: June 25, 2019, 10:19:25 AM »
Is it possible to pull the wire off without dropping the tank?

Offline MIKE S

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Re: Another Fuel Gauge Question
« Reply #3 on: June 25, 2019, 02:12:33 PM »
It's virtually impossible to get your hand over the frame rail to get to the wire or the hoses. I just changed the fuel pump in the tank of my 87 this weekend. How I access it is take out the four cab mounts and put a jack under the rear center of the cab. Raise it up about 4-5 inches and block it between the body and frame at the rear mounts. You will have enough access to the sending unit. Don't leave it in park. In fact take the shift rod off of the steering column. It will bind and possibly brake the shift bowl.

Offline VileZambonie

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Re: Another Fuel Gauge Question
« Reply #4 on: June 25, 2019, 05:10:05 PM »
Follow the wire. Since you truck was equipped with dual tanks you will find a connector for the pink wire which is not on top of the tank. If you do need to remove the sender, I would suggest sliding the bed back for easier access.
,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

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

Offline 75gmck25

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  • 1975 GMC K25 Camper Special, 350/TH350/NP203
Re: Another Fuel Gauge Question
« Reply #5 on: June 26, 2019, 05:27:38 AM »
These trucks were designed so that a single tank truck could have an aux tank added by the dealer, so the electrical lines to the sending unit should have pop-apart connectors at several locations that are easy to reach (my connectors are round). 

For example, on my truck the sending unit has a round post connector for the power wire and a spade connector for the ground. Both wires thread through a grommet on the frame and end up inside the frame where you can reach them.  The ground wire is grounded to the frame, and the power wire has a pop-apart connector.  When they added an aux tank they just pulled that connector apart and added the wires running to the tank switch, so that it would switch between left/right sending units when you switched tanks.

My sending unit wire to the gauge and primary tank is tan, and the one to the aux tank is tan with a white stripe.  I don't know if they continued to use that color code in later years.  Some of the wiring is confusing because the dash switch has to be elecrically in between the two tanks.

Bruce