Fuel level increase overnight

[mf7lakes]

Front tank at 3/4 when parked -- next morning now showing overfull & rear tank now shows 1/2 -- rear was full day before

Selector valve gone bad???

Was parked on slight incline -- nose down

 

[Clb]

That's a new one on me for these rigs...
But yeah kinda has to be in the switching/returns...
Try repeated tank changes, also back blow the tanks, open the caps and run low psi air from the front

 

[Cubey]

Sending unit or gauge going wonky?

 

[Clb]

Both tanks at once tho???

 

[Jesus Freak]

I'm calling it that the sender is reading bad unless you got fuel on the ground from the vent leaking..... or possibly the gauge itself..... sounds interesting, keep us posted!

 

[Cubey]

Both tanks at once tho???

Gauge could cause it. or wiring between the gauge and selector valve. the valve just switches which sending unit is connected to the gauge.

but i have seen IDIs with slightly wandering fuel gauges like that too, as i recall

 

[IDIBRONCO]

but i have seen IDIs with slightly wandering fuel gauges like that too, as i recall

Mine does. Sometimes while driving, even several times, other times it will have a constant reading while driving and then have another reading the next time that it's started to be driven. Mine seems to be at the same times as the other gauges though so it's probably the famous voltage regulator behind the dash. This is how my gauges usually look. The picture is blurry because I took it while I was driving. When the oil pressure gauge reads lower, I get kind of nervous while transferring fuel into the front tank. It's easy to overfill it when this happens. I've tried different oil senders and it still reads like this.

 

[DirtyWood]

I write down the odometer mileage at every fill-up and base my range on that mileage. I don't trust 30+ year old gauges and sensors. At least the odometers seem to keep working in these things--knock on wood.

 

[Brian VT]

That's how I decide when to refuel.

 

[mf7lakes]

So, didn't drive it today, but parked it overnight, this time with the nose up. Then I exercised the FSV about 8 times -- each time I could hear the solenoid/motor moving.

The gauges have not changed since shutting down on Saturday. So it ain't draining the other way -- and there's no diesel on the ground.

I'll drive it tomorrow and let y'all know. I'll fill up the rear tank (love me some $$$ diesel) also.

 

[mf7lakes]

Put 4 1/2 gallons in the rear tank today -- gauge came up to 3/4 full now -- guess sender & fuel gauge reading correct. I'll drive it around some more to get the front tank back down again and then park it nose down again to see what happens

 

[Clb]

For grins throw a can of techron in each full tank and let it sit so it can clean the rheostat for the senders...
mine went stupid once and that and a dose of bio cide cleared it up.
The biocide was just in case...

 

[mf7lakes]

PowerSvc BioClean + Stanadyne

 

[mf7lakes]

Left it parked nose down for 48 hours -- tank levels in either tank did not change --- so my verdict is that FSV was stuck somewhere in-between tank selection positions.

I'll exercise that switch/FSV more often and frequently.

 

[Jesus Freak]

Ahhhhh.... a happy ending! Thank you for finishing the story @mf7lakes !!!