Please donfirm that my gas guage is "normal"

[sdyck]

'72 240Z

My gauge sort of works, when I fill up it goes to full, but then it drops quickly to half full hangs around there awhile then slowly drops to about 1/8 full which is generally when I refill it. The odd thing here is when I fill it from 1/8 full I can only add around 10 gallons. Which means I have 5 or more gallons left.

At first my searches led me to believe that my float may be filingl with gas and acting strangely as a result> but then I ran across this post from an admin over at Hybrid;

"The shape of the gas tank makes the first 1/2 of the tank go really fast in relation to the last half on the gauge. There is a lot more volume in the tank when it reads the bottom 1/2 of the gauge. Also the fuel senders are not the latest and greatest design and they tend to not be accurate, especially after 30+ years of service."

Can anyone confirm that?

ThankZ

Edited September 8, 2014 by sdyck

[Zed Head]

That's about what mine does, 1976 280Z. It will sit right on 1/2 full with the trip meter from 100-150, then drop to just above E at 220 miles. So I get 100 miles above 1/2, 50 miles at 1/2, and 70 miles below 1/2. Consistently.

Then I can get about 12 gallons in on a refill, so apparently I'm 5 gallons paranoid (early 280Z's have a 17 gallon tank). I've never seen the red warning light come on, don't even know if it works. I've hit 280 miles on the tripmeter, but it makes me nervous, even though I know that fuel is in there. Always calculates out to between 18.5 - 20 mpg.

I need to take it down to the red light some day.

[olzed]

I can confirm that my 240's tank still has fuel when the gauge needle does not move.

Tank was sucked dry of fuel when at the paint shop, and i drove it home not noticing.

[siteunseen]

I agree. Back when I had my first Zs the gauge would go waaaay past E. Now that I can afford to fill them up, when they're on or near E, they only hold about 10 gallons.

I'm learning the gauges in these cars were/are their shortfall.

[jfa.series1]

I had a similar experience recently after a rare fill-up. While on the road I noticed a pretty rapid drop in the gauge, figured I was really burning a lot of gas, and had the "aw sh-t" moment. Then the gauge slowed noticeably and I realized it was the step in the fuel tank causing the different rate of change in the gauge. Most of the time I only give my little garage queen enough fuel for local events and I had completely forgotten the effect of the tank shape. I really need to check my mpg and how much gas I can get into the tank.

[Bonzi Lon]

The Hybrid statement is correct, the tank is 'L' shaped, more fuel in the lower portion than the top. Also, the fuel sender unit is not wired for an 'L' shaped tank, the resistor windings, but more like a rectangular one.

During the refurbishment, the tank was boiled, sealed and new sending unit, works as described, top half of the tank goes real quick on the gauge, then slower for the last half. On long trips I have found it will run about 2 1/4 gallon per hour, 26.5mpg highway, so that can help with calculating amount of fuel left. I've ran the needle down to cover the empty hash mark, but still had enough to get to the station. Would still like to know how low it can go before the engine quits.

Bonzi Lon

[sdyck]

Thanks, good news that I don't have anything to fix, bad news that I can't rely on the guage.

My calc's show I'm getting 15 mpg city, ( I'm in nead of a full tune), I guess I'll have to get used to setting the trip meter rather than relying on the guage. I should be able to get 200 miles out of it and leave at least 2 gallons.

[bartsscooterservice]

I have a similiar thing, and I installed a new " NOS from Ebay" fuel sender since I was refurbing the tank anyhow. Funny the old one seemed more accurate to me ? Also does anyone have problems when filling up, I find the filler neck very small for today's fuel filler pistols from the gas pump, I cannot go full " throttle " on the fuel delivery..

The 240Z's float reminds me of the one I find on the Chinese scooters today...sometimes they work great, sometimes not.. but I have found this problem on the scooters to be a small clip that has been pushed down to hard in the factory making the float not move easily, so with a small screwdriver I go under the clip to give it some room, and most floats work again after that.

Edited September 10, 2014 by bartsscooterservice

[sdyck]

I can go "full throttle" when filling but it does tend to click off a couple of times, so I'm never sure I'm actually full.

[LeonV]

I always fill the Z tank slowly. Have to do the same on my S2000, strangely enough.

[TheCrazySwede]

Same thing in my '77 280.

My gauge isn't fully functional, though. It never goes past half (the needle stays in the middle) even after a full-refill. Then, after about 150 miles, it drops and hovers right above E. To refill it takes around 10-11 gallons.