Where did the fuel go?

[supersisu]

Here's the story:

It got pretty cold here is Chicago over the weekend, about 0 F. Freezing rain, then snow. I didn't drive for a few days, and had my old battery inside to keep it warm. I wanted to drive to work Tuesday morning, so Monday night I went out to plug in my engine block heater. It had not been working well, it turned out the cord was almost severed (contact with the motor mount?). So I spent a nice long hour in the cold and dark soldering the cord together. Plugged it in and heard the heating hiss. So far so good.

In the morning I put my old warm battery in, it barely cranked it over. Okay, no work today, walked to the autoparts store I don't like (it's just the closest), bought a battery, stuck it in the car and cranked over the warm engine. Nothing. Just crank, crank, crank.

Okay, no fuel. Checked that the shut off solenoid had power, swapped it with another, nothing. Finally opened the fuel return banjo bolt, looked in the fuel pump, bone dry. Got some ATF, primed the pump, started up right away. (by the way, the hardware store guy asked what kind of ATF I wanted, regular or the kind "with grit in it", I chose regular).

It's a mystery why the pump was dry. I didn't have a lot of fuel, the needle was just above the red, about 80 miles into $10 worth. I'm wondering if the cold created a vacuum in the tank and pulled the fuel backwards out of the injector pump. Keeping a pretty full tank, a quart of ATF, and a 17mm wrench in my car now. Any thoughts?

Thanks,
Erik

[bscutt]

The tank is vented so it should not create a vacuum. Maybe the cold caused seals to shrink and allowed fuel out somewhere? Or possibly the tank vent is somewhat clogged but I doubt it. Shaft seal or cold start seal might be leaking slightly. It's pretty hard to diagnose this in the frigid cold. A quart of ATF is a good thing to throw in the trunk as you said. It's also handy in case you happen to run out of fuel some day in which case 3 or 4 quarts are nice to have. A few years back a local dollar store had ATF for a buck a quart and I used to keep 2-3 quarts in the back for that kind of emergency.

[82vdub]

It really is hard to say where it went. It's possible that there's a restriction in the fuel line, creating a suction when you turn the car off. It's also possible that some of the seals on the IP are worn allowing the fuel to siphon back to the tank, or a fitting on a fuel line (those little barbs on the injectors are good for this) is loose or cracked.

[vwkook]

Mayhaps the fuel in the filter gelled?

[Fatmobile]

If one of the small lines between the injectors starts leaking air while sitting;
all the fuel can syphen back to the tank.

[supersisu]

Fatmobile, I like that answer! I'm a fan of the siphon principle and it's the only thing that makes any sense to me. It never happened before and it hasn't happened since (but it hasn't been that cold again). The new battery and repaired block heater help a lot too. Thanks all for the input.

Erik