I purchased a 1968, 302, Auto Cougar. The previous owner had put a brand new fuel tank in it. When I fill up on Empty, the most I can put in is ~11 gallons. Now according to the reprint manual I got, it says the standard tank is 17 gallons. I’m getting 13mpg so I’m getting a little tired of filling up every 10 gallons.
My questions:
Is there a way by looking at the tank how big it is (# of gallons)? Did the previous owner put a smaller tank on?
Is there a way to tell if the gauge is just not accurate? I’m hesitant to just run out of gas to try that theory.
The temp. gauge runs on the high-normal side but my mechanic says it’s actual temp is normal. I have no idea it that has any relevance but thought I’d mention since the temp and fuel gauge are in the same cluster.
Sounds like your PO also put in a new sender, maybe even the same sender I put in. I’m seeing the exact same symptoms. For me, I can run it down to the bottom of the red by empty and still have gas. When I run out of more pressing things to work on I’m going to experiment with adding a ceramic resistor at the sender connection point to see if I can get the gauge to read correctly.
My engine temp also always runs to the right of center, not in the danger zone or anything, but always to the right of center.
Measure the length, width and height of the gas tank. Multiply these three numbers together to obtain the volume in cubic inches. For example, if the length is 26 inches, the width is 10.5 inches and the height is 17 inches the volume in cubic inches is 4641 cubic inches.
Multiply the amount of cubic inches times .00432900433 to obtain the capacity of the fuel tank in gallons. This is the constant number to convert cubic inches to gallons. For example, 4641 cubic inches times .00432900433 equals 20.09. Round the number to the nearest whole number. This size tank holds 20 gallons.
You guys are awesome. I feel better knowing I’m not the only one with this issue. Not sure why that makes me feel better but it does. According to my rough measurements, 30Wx21Dx7H I should have roughly a 19gallon tank. At least I know it’s not 12 gallons which is about what the gauge is saying it holds. I GREATLY appreciate your great suggestions. Thanks!
Many times the problem with the fuel gauge reading 1/2 tank when full is; the float on the fuel sending unit, in the tank, has a pin hole in it,…the float will then be partially, if not completely be full of fuel and you gauge readings will be off,… the float will be submersed in the fuel in the tank and not floating on top of it, making the gauge read less than the actual level.
I specifically tested my float for this before installing the new sender a few weeks ago. I removed the float from the sender and held it underwater in my kitchen sink for several minutes. It didn’t take on any water at all. So I am inclined to believe the issue in my case is related to the electrical resistance of the sender, not a pinhole. But I did the test because I read here about the pinhole issue.