How much fuel is in my tank?

[John Mc]

Guys, I don’t have a scope, so anyone have a trick to find out ho much fuel is in my tank? I put a hose down the filler tube and it sounds like it was empty, or nearly so. I have dropped fuel tanks before when I THOUGHT it was empty, only to find out I have a half full tank over my head.

[1Bad55Chevy]

Your car has a flat tank under the trunk floor right?

[John Mc]

Yup, pretty flat

[1Bad55Chevy]

That's super tricky because anything you put in there will lay flat across the bottom of the tank so it's impossible to figure out how much fuel is in it.

Are you trying to drain the tank? If so I would recommend one of these.

https://www.harborfreight.com/fluid-sip ... ekQAvD_BwE

I had one similar to that before, I stuck a piece of hard plastic tube on one side and would shove down into gas tanks when I had to replace fuel pumps. Now I have a under hoist transmission jack so it dosen't matter how much fuel is in the tank.

[frasern]

Sorry 55, but it still matters, I just changed a tank in my diesel truck on a hoist, with a transmission jack, and that fuel sloshes, it changes balance very quickly. Do-able, but easier with the fuel out.
I used an electric pump to transfer as much as I could, but you can also dis-connect the fuel line at the engine end and route it into a jerry can, it will gravity feed until empty. Sometimes feeding a hose through the filler tube is difficult, even more so on newer vehicles.

[Lee]

You could use the Helmholtz equation, some compressed air blown across the filler neck, and one of the free apps to determine the resonant frequency of the air volume remaining in the tank

Or not

I’d get some clear tubing and attach to the fuel line. Raise the clear tubing next to the tank until the level matches, and you can make an estimation. I’ve used this trick to determine float level in the Model A.

[frasern]

Spoken like an engineer!

[Dan Szwarc]

Your car has a flat tank under the trunk floor right?

Not 70s continentals. The tank is upright behind the rear axle in front of the trunk.

But John’s question intrigues me. Fuel gauge doesn’t work?

Fuel weighs 8lbs per gallon. When the needle hits empty (initially) there’s still 6-8 gallons in there. Ford left plenty of cushion for our dads to say “There’s plenty of gas in there!”

The best way to tell is to pull the fuel sender and use a hose gage (for wetness from there), but why not pump it out from the hose using a drill-pump?

[John Mc]

Dan and all, yes the gauge works (from what I can tell, it did jump to full when grounded) and it currently shows empty, I did stick a clear tube down the filler tube and using it like a dipstick, it shows almost nothing………..just don’t want to be surprised!

[John Mc]

Speaking of gas tank removal, I’m faced with a challenge. Both of the caged nuts are free spinning. I’ve tried the “two nuts” approach and now I’m rounding off the nut! Normally I would just grind the nut off but I’m very hesitant to do that with a fuel tank above my head. It might be the only way, am I missing a trick here?

[Dan Szwarc]

The trick is you prop the tank up with a 2x6 across the width with a jack in the middle holding it up.
Then you can safely lower the tank.

[Dan Szwarc]

Take a wire brush to those threads and clean clean clean before you try again.

There isn’t a cage nut in the body, but a slot. The bolts have a square section below the head like a carriage bolt. The bolt-square is probably rounded because they are not hardened beyond grade five.

You can see a metal hold-down flange of metal which helps hold the bolt don’t into the slot when you tighten the nut.

I’ve dropped about 5 tanks in my life.

[TonyC]

Judging from the picture, we are talking about one of the '70s cars? Then yes, the tank is vertical. I'm guessing it's never been removed since initially installed, considering the rust buildup. It's not an easy task to remove seized tank retainers...but not impossible.

The way I determine how much I have in the tank, given that the newish sending unit is about as off as a GM unit, is to note the needle's position and compare with the actual amount needed to fill the tank at any given time, knowing in advance the maximum capacity of the tank, which the owner's manual should indicate. My needle reads about four gallons lower than the amount actually in there. It's accurate at the Full mark, but as the gas burns off the needle drops faster than the actual fuel supply.

---Tony

[Dan Szwarc]

More suggestions: dremel with a brown stone disk across the bolts and a large box fan blowing directly into the area.

Or cut the straps at the bottom. Same big fan.

Ive dropped tanks with 1/4 tank of gas all by myself. Not impossible. Tip the tank away from the filler neck when low enough and it contains the fuel. Raise the car higher after to slide it out without more tipping.

[frasern]

I think your question is how to remove it without sparks. Drill a small pilot hole, sideways into the hex, then a larger one, then break the nut open with a cold chisel.
But that is un-needed, unless it is leaking nearby.