Verify defect fuel sending unit

[13matsc]

Hi guys,

Original dual tank setup. Right side tank fuel gauge peaks at 3 o clock when selecting that tank. Removed the chassis ground and worked everything with the wire brush, then reattached. Still same problem. This verifies that the fuel sending unit inside the tank is faulty? Check my picture to see if the ground cable i worked on.

Left hand side works as it should. Switch, the switching valve and the resitor on the gauge itself should be OK?

Would like to be as certain as i could before dropping that tank, does not look like a fun job.

 

[Grit dog]

No expert but there’s a ton of info on here if you search. 3:00 position = open circuit to gauge iirc. 9:00 position = grounded out.
One suggestion though, I believe it’s easier to remove (or at least unbolt and slide back) the bed. Unless you have nothing or no one to help lift or slide the bed.
Just my opinion. Also makes it easy to remove both senders, inspect , clean, fix grounds etc.

 

[fast 99]

The hoses are a PITA. Either unbolt bed as described above or back 4 cab bolts and block it up. I tried unbolting beds on a couple, but the carriage bolts just spun. Was less work to jack the cab up.

 

[Ricko1966]

IMHO pulling the bed or cab to change a tank is a bunch of extra work. I always have to drill the heads off the bed bolts. I'd unbolt the tank,brackets and all drop it far enough to reach over with a pair of compound leverage cutters and cut the hoses in the metal,use new hose going back in. @fast 99 how did you deal with the spinning cab bolts? I have a feeling that's going to be a problem I have in the near future.

 

[13matsc]

Thanks. Looks like dropping the tank is the best alternative for me, if needed. I will be checking the wires to and from the sending unit (if I can find them).

Pink wire from the dash, through the firewall and all the way back to the tank switching valve? From there it changes to tan, and then goes to each tank sending unit?

85 model with factory dual tanks.
Weird that the sending units are placed in such a place - difficult to reach, yet open to all the elements.

 

[dsteelejr]

Thanks. Looks like dropping the tank is the best alternative for me, if needed. I will be checking the wires to and from the sending unit (if I can find them).

Pink wire from the dash, through the firewall and all the way back to the tank switching valve? From there it changes to tan, and then goes to each tank sending unit?

85 model with factory dual tanks.
Weird that the sending units are placed in such a place - difficult to reach, yet open to all the elements.

I replaced the sending unit in my ‘80 K25 last month. I removed the bed bolts and pulled the bed back and that was a PITA in itself. I had to use an induction gun to get the bolts red hot to loosen them up from the corrosion. Just a big pain and it didn’t completely uncover the sending unit. Part of it was still under the cab. You could replace hoses and wires that way, but if you’re replacing the whole sending unit, which I did, you’re better off dropping the tank. It’s just four bolts through the frame.

On a side note, I replaced the bed bolts with new ones from the LMC Truck bed bolt kit. Waste of money. Two of the bolts were at least two inches too long and I couldn’t use them. Ended up reusing two factory bolts. Before buying the LMC bolts I considered buying carriage bolts from Bolt Depot. It was cheaper than LMC’s, but I figured LMC would probably be a better match, but no. The factory bolts have a larger head than standard carriage bolts and was hoping LMC’s would match the head size, but they don’t. They’re overpriced, standard carriage bolts.