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What could it be?

My car started stalling out like it’s running out of gas. It had a half tank and I was driving about 75 in cruise. It sputtered to the gas station and I filled it back up. The problem stopped. My mechanic can’t find a problem.

I’m far from a mechanic and use this site for advice just like everyone else, but I encountered this problem on a company van once. It was a bad sending unit and the gas gauge would not go below 3/4 of a tank. I guess the question would be, did it take only half a tank of gas to fill it up when you stopped?

Yea it only took half a tank. But it has ran completely out with out being on E twice. Nothing consistent though.

As I said, I’m not a mechanic, just a “fix it when it’s broken and I have to” guy but if it only took a half tank to fill it up, it’s probably not the sending unit. It could be the fuel pump, clogged fuel filter, or a bunch of crud in the gas tank. I’ll let the pros tackle this one.

You may have a weak fuel pump. When a tank is full it has “head pressure”, which is the weight of the gas assisting the pump in moving fuel up the pickup pipe and into the fuel line. I could be that when the gas drops some and the head pressure lowers, the pump lacks the oomph to pull the fuel up itself and maintain line pressure. A clogged pickup screen could manifest itself this way also.

It’s also possible that your tank is unable to breath air into replace the fuel being pumped out and a vacuum is developing in the sirspace in the tank, preventing the pump from maintaining proper fuel line pressure. This can be caused by a kinked line or a saturated charcoal canister charcoal bed. The tank breaths in and out through this bed of activated charcoal. If it’s saturated it’ll choke the system.

An '01 has an OBDII system. You should have at least tripped a fault code when you stalled, and a charcoal canister problem should trip an EVAP system codes. Did you get a CEL? What were the codes?

Did your mechanic check the fuel line pressure?

One other thought: if it happens again, take the gas cap off and reinstall it. If the problem disappears it’s a good bet that a vacuum is developing.

Thank you for the info. Strangely enough I’ve since ran it all the way down below a quarter tank without any problems. I added some fuel system cleaner again. When it originally happened I was in cruise control. I wonder if the cruise system could have caused a temporary vacuum. There were no codes or sensors either. That’s why this is so weird. A fuel pump would cause a consistent issue and most everything else should pop a code.