Firstfives.org

Now that I've mostly solved the hot-running engine issue, another one has crept up. It's likely been this way for a while, but I could never drive it long enough to notice.

From a full tank of gas, I'm only getting ~150 miles. To help y'all better diagnose, the head was replaced about ~600 miles ago. Plugs are new, as is air filter and fuel filter. O2 sensor is likely original to the car (103k miles).

Car is a '79 528iA.

leaking tank?

Unlikely. It sat for a month while I tracked down the overheating issue, and the fuel gauge stayed at the full mark the entire time.

Ok, but perhaps the crack is above the line where your gas level was at that time and after filling up it quickly gets down to the level of the crack?

Sure, not probable, but possible.

If you are truly filling up a 16.4 gallon tank and it takes 150 miles for the light to go on, that is much too fast, as you know, even if you're doing all city driving. Aside from major injection system issues that would cause black smoke to emit from your exhaust, I'm not sure what could make things so bad. Unless it's a "perfect storm" confluence of super low tires, all city driving, lead foot, bad gas, bad injectors, leaky tank, plugged up cat...

How does it run?

Oh, and start with O2 sensor if the tank's not leaking.

If that's bad, that alone will help some.