Gas tank sender unit

[tdeming]

I want to replace my stock sender unit that goes with the original gages. The sender unit on my tank has 3/8" tubing, and all of the suppliers show a replacement unit with 5/16" tubing. Has anyone found a correct replacement unit for GMC trucks?
Thanks,
Terry

[FetchMeAPepsi]

I cant help you with the sender but is yours flat out broken? You might be able to clean it up and have it work. Carb cleaner works wonders if you mix in two to three days of thyme.
Ha ha, get it? thyme (time)? It's a recipe for success

[tdeming]

Its broke. The rheostat is worn out. If anyone has a working one for sale let me know.
Is anyone using the sender unit with 5/16" tubing on a 305A? It seems to me that would starve it and cause a bunch of problems.

Terry

[tommyduncan]

I bought a sending unit and hooked it up a couple months ago. I didn't notice any issues but there was a lot of fumes involved.
I will look a little closer when I get home.

[T Herder]

You can use the 5/16 sending unit with no problems. My 305E is fuel injected with 5/16 supply and return lines to the stock tank. It won't starve. Here's the procedure I wrote for another forum to add a return line to the stock tank.

Sand an area of approximately one inch diameter to bare metal on both sides of the new units mounting plate. Drill a 3/16” hole in the mounting plate and remove any burrs. Support the mounting plate on the internal side of the plate with a 9/16” six sided socket, the six sides towards the mounting plate. Take a 5/16” diameter tapered drift punch and drive it through the hole to form a tapered flare recess. This recess will be on the outside of the plate. Using a tubing bender, bend a 5/16” steel tube to parallel the fuel pickup line ending at the same bottom level BUT returning to the OPPOSITE side of the tank. Bend the external side of the return tube down to parallel the feed line. Carefully work the new return line through the 5/16” hole to what you THINK might be its final position. Then try fit it into the tank to confirm it will install with no problems. Once this is accomplished, Silver solder the 5/16” tube into the mount plate using 45% Silver solder.
If you’re hesitant to try this, practice first with a piece of scrap sheet metal and scrap tubing of the same gauge as your new replacement mounting plate.
Best regards,
T Herder

[tommyduncan]

Originally Posted by T Herder

My 305E is fuel injected...
T Herder

Are there any write ups on this? I would love to know more about it!

[GMCNUT]

I do not understand this thread - I ordered a replacement fuel tank sending unit from LMC truck or somebody and the catalog just showed as being for Chevy or GMC, and it works fine....there was no 5/16" vs 3/8" choice to make in my case, so maybe you should just buy a new sender from LMC and be done with it?

[tdeming]

Thanks for everyone's help on this. I don't want to replace all the gas line tubing to the filter and carb. So I have decided to order the available sender unit and remove the new rheostat and float and silver solder it to my old fuel pickup tube.

Terry

[David R Leifheit]

Originally Posted by GMCNUT

I do not understand this thread - I ordered a replacement fuel tank sending unit from LMC truck or somebody and the catalog just showed as being for Chevy or GMC, and it works fine....there was no 5/16" vs 3/8" choice to make in my case, so maybe you should just buy a new sender from LMC and be done with it?

What size was the one you got from LMC?

GM used two different sizes. The first time I replaced mine I pulled one out of a wrecked chevy of the same year... then had to go back and get the hard line because of the size difference.