Tanks are acting empty at about 1/3 full

[Jer4sports]

Hey guys. I just drove my 78 Chieftain from Colorado to Arkansas. It made it safe and sound with a little bit of TLC.  About 150 miles in, the main tank started acting empty.  I switched it over to aux tank and all was fine for a while. When I filled up, I switched back to the main and about 50 miles down the road the fuel started pumping inconsistently into the carb.  I switched to the aux tank and it did the same thing.  I pumped the gas for a while until I got to the next gas station.  For the next few hundred miles, I would go about 20-80 miles with it running fine after I filled up and then it would do this again.  Finally, I couldn't stand it and was sick of doing 40 mph up hills with semis passing me at 70 mph.  Not knowing a ton about auto mechanics, I did a little research and decided to replace the fuel filter and put in some fuel treatment.  Found a Walmart and after all that, the 3 dollar filter did the trick!


However, my main tank (not sure about the aux tank yet) still starts acting as if it is empty around 10-15 gallons left.  That is, if the tank is actually 36 gallons like the manual says. My fuel gauges do not currently work so I am basing this on how many gallons I have to put into the tank during fill up. I will fill up until the gas overflows.


Any thoughts or suggestions? Thanks guys
-Jeremy

[legomybago]

It's possible your engine fuel line is tapped into the generator port on the fuel tank sending unit. They do this with generators to prevent you and me from running the tank dry while camping and using the genny. Leaves some fuel in the tank so you can drive to the gas station. Only one way to know....Drop the tank down and investigate...Your probably going to be doing this anyway, sounds like you should replace ALL your rubber fuel lines too..

[eXodus]

did it ever work ?

I like that idea the former owner probably messed with the fuel lines and just connected wrong between engine and gen-set.

all fuel lines look the same.
You can just try it, run your engine until it makes the weird stuff, then start the gen set and let it run until it dies - then refuel.

Fuel sending unit defect or just connected wrong