yesterday was the first time my 94 940 ever left me stranded. I was running very low on gas and foolishly didn't notice until it was nearly on fumes. Before it ran empty I pulled over, got a lift home, got my fuel can, and added gas. I drove to a gas station and filled it up.

A few hours later I drove it for five minutes, ran an errand, and upon returning to the car, it wouldn't start. I cranked until the battery was basically dead. It wouldn't catch at all.

It has spark, and I can hear the main fuel pump spool up when I key on the ignition to position II. However, the main pump sounds a little funny, and it has always made an unhappy sound when the fuel level is low. Four years ago I replaced the in-tank pump myself because this main pump sound led me to discover that prepump was dead.

I'm wondering how I can diagnose whether the issue is with a dead pre-pump, an almost dead main pump (can it prime but still fail to produce sufficient fuel pressure?), or some other problem. Previously, when I discovered the in-tank pump was dead, I was able to listen with my ear to the gas filler tube. Now that the car won't run, is there another way to test for in-tank pump functionality without taking out the whole sender unit (that wasn't fun). I.e. Should it also prime for a few seconds at key-on?

I'm also wondering if there could be an air bubble in the fuel line before the main pump that is starving the main pump of flow. A friend suggested that I jack the rear of the car and remove the fuel line just before the main pump--would this help to remove an air bubble and restore flow to the main pump, or would the pre-pump need to be operational in order to do so?

sorry for the long post. Any suggestions are appreciated.