Gas tank size after conversion?

[86Scotty]

That is weird. I guess it's just luck of the draw. I started noticing it first on delivery vans I drove in the 90's and then when I kept accumulating them personally since I've been active here I've noticed the same. Maybe you have the only one ever made that is accurate?

[JWA]

Any fuel level sending unit that moves in an arc will not seem accurate---the phenomenon where you drive 10 miles and the gauge drops from full to 3/4 then you drive another 300 miles and it barely moves is simply a function of how the float moves and how the vehicle electronics read the resistance value the level's potentiometer output.

Its annoying but giving the simplicity of the fuel level sending unit we're not going to really improve on how it works. For me the simple solution is NEVER let the gauge read below 1/4 tank--mileage from topping off to that point is of no concern to me---are we there yet?

[TomsBeast]

Originally Posted by JWA

Any fuel level sending unit that moves in an arc will not seem accurate---the phenomenon where you drive 10 miles and the gauge drops from full to 3/4 then you drive another 300 miles and it barely moves...

Yep, it amazes me at how they can design systems with traction and braking control at each individual wheel, but a linear reading fuel level system is that hard. Maybe just unimportant to sales.



as a side note; I had this F350 dually with factory twin 17 gallon tanks... at 5mpg towing, I was pulling into a filling station every 150 miles.


You could watch the needle move, I swear

[JWA]

Originally Posted by TomsBeast

You could watch the needle move, I swear

Reminds me of a '69 Chevy one-ton van that was like that too---had the 350 CID engine which was okay on MPG's but the wonky gauge and sending unit wasn't reliable at all. It never gave a false reading but the lack of accuracy was bothersome.

And yeah I'm with youi on perhaps a vertical float rather than the swing-arm types. I can't help thinking such a design would be less long-term problematic as the float would rise and fall more in line with the fuel level at least as its shown on the gauge.

Oh well---Its Christmas so we can't gripe too much today.

[Orv]

Originally Posted by TomsBeast

Yep, it amazes me at how they can design systems with traction and braking control at each individual wheel, but a linear reading fuel level system is that hard. Maybe just unimportant to sales.

There are also advantages to simplicity. I had a Mercedes diesel with a true linear fuel level sender, because the Germans over-engineer everything. It broke, because to make it linear they stretched two very fine wires vertically and had the float ride up and down along them. I replaced it with a cheap universal GM sender, which wasn't linear but was robust. (I used a GM sender because it had the correct resistance range, although the full vs empty resistances were swapped. I solved this by flipping the float assembly over.)

I'm also reminded of a trick question you sometimes see on written exams for pilots: "At how many points does the FAA require fuel gauges to be tested for accuracy?" The answer: One. They're only required to be accurate at empty.