Stalling and loud fuel pump

My 97 GMC Jimmy is having problems with a very loud fuel pump and stalling while approaching a stop. The fuel pump died last summer and we replaced it. It worked fine until about a month ago. We put in a bottle of fuel treatment that helps with any water and ice in the system. After that the fuel pump got very loud and eventually we started loosing power and barely made it home. We changed the fuel pump again and it was fine for a few days. The fuel filter seems to be fine. When we got to about a 1/2 tank the fuel pump got noisy again and the car started stalling while approaching a stop. We fueled it up 3 times already and it seems to be fine (except for a loud pump) for the first 150 miles, then it stalls. We are thinking it might be a vaccum switch problem. We did have a vaccum code a few months back, but it hasn't come on again. Any suggestions?

fuel filter seems fine?

How do you know?

CHANGE IT!

We just changed the fuel filter and fuel pump and the problem is back again. It was working fine for a day, but something is causing the fuel pump to fail. It is OK now but when the fuel level gets low, it will stall when stopping. We also got a evap emisions control system code. Any ideas? Could it be the fuel regulator or a vacuum leak somewhere?

What code are you getting?

What code are you getting?

Code 440

Code 440 and I also notice that when I come to a stop, the RPM increases about 500 rpm for a few seconds and then goes back to normal.

Check evap canister purge solenoid.

I found the problem with the stalling and loud fuel pump. We changed the fuel cap last fall and it never clicked tightly close. We were able to finally close it tightly and the car has not stalled since. We still however get the code 440 but did not have any other symptons until this week. I was driving on a 5 hour trip and while driving 70mph the rpm jumped up and down about 500 rpm's and the car jerked. I stopped the car checked all fluids and did not see or smell any leaks. I drove another 200 miles before it happened again. I stopped again and then continued home without any problems. Could this be the control solonoid like you suggested before or a transmission problem? The transmission has only 40,000 on it. Thanks.

Evap solenoid is not closing which will act EXACTLY like a vacuum leak.

Vacuum leak will cause rpm's to yo-yo, but only at idle - NOT at highway speed.
Not likely a tranny problem...
Fuel regulator (pressure regulator???) not likely a problem either...

Vacuum leak will cause rpm's to yo-yo, but only at idle - NOT at highway speed.
Not likely a tranny problem...
Fuel regulator (pressure regulator???) not likely a problem either...

Yes it will, when the EVAP solenoid is going on and off, it will cause the surge.

Yes it will, when the EVAP solenoid is going on and off, it will cause the surge.

Thanks for your help. We have a evap solenoid on order and will let you know how it works!