While Driving home on day, On the highway My 2003 Chevrolet Avalanche (1500 5.3 Liter) The Engine started making a Coughing sound as If it was running out of gas. The gas was full, When I got off the Highway I pulled into a Walgreens parking lot to check out the Problem. When I got in and Turned it on it sounded fine, until I let it run for about 25 seconds when it started backfiring. I revved up the Engine and put it in Reverse. When I put it in reverse I hit the gas and the whole Truck lost power, and turned off. I am thinking that it is a Fuel Pump problem, Please help. Any Suggestions?

 

Do a fuel pressure check..