1996 Volvo 960 stalling and other maladies

A short while ago my poor car (she has 258,000 miles on her) decided not to start. I brought to my mechanic and, after roughly two weeks of waiting I receive word I can come pick her up, it was a faulty fuel pump and it’s been replaced. So I make my way across town and my mechanic tells me with an anxious smile that it was running when he called me and to come back tomorrow.

I do so and he says the culprit was it was out of gas, and he kindly put 5 gallons in it for me which I will notice on the bill. But when I head to the gas station it only takes 6 gallons – it’s a 21-gallon tank (oh yes, he broke the gas gauge as well).

So now a couple things occur: 1. The car stalls when the gas falls below a half-tank, and 2. When I drive over a bump on the Interstate the car will often stall for maybe one second and then come back on.

Did this come about (the gas tank stalling, the bump stalling and the broken gas gauge) via the replaced fuel pump? Any ideas? I am bringing the car back to this mechanic with the expectation that he fix everything free of charge (whether he yet knows it or not) but I wished to get an opinion of the resident experts here.

Thanks for listening.