How can one check to make sure your problem is the fuel pump. i disconnected the line at the fuel filter and had no fuel flowing out when trying to start vehicle is 2001 GMC Safara Van

The logical thought on this would be to ask if you changed the filter, also if the pump is electric and in the tank, was the strainer changed? If EFI have you checked fuel flow before and after the fuel pressure regulator? Can you hear the pump running? Did you check the fuse for the fuel pump?
I'd start by making sure the pump has voltage, then disconnect the fuel line before the filter and see if there's any fuel in the line. Then have someone just turn the ignition on momentarily to see of the pump is pumping. If it isn't you still have an issue with the pump. Finally, if you have an in tank pump, and have installed an external line pump to save bucks, this doesn't always work because there are check valves in some internal tank pumps that prevent fuel flow.

its inside your fuel tank part of the fuel pump assembly

are you sure it was the fuel filter the actual problem? may be the fuel pump went out? check to see if you have fuel in the tank some mechanics put some fuel in the fuel filter just like they do with the oild filter.

No pressure at fuel rail either mean a clog in the fuel lines or filter...or a failed or incorrectly installed pump. If you have voltage at the pump when you are cranking the engine over recheck pump and fuel filter. also try applying shop are to the fuel lines when disconnecting at pump and fuel rail to clear any clogs.

Fuel Pump-Mounted Filter

1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
   
2. Properly relieve the fuel system pressure.
   
3. Remove or disconnect the following:
   
   • Negative battery cable
     
   • Fuel pump cover plate
     
   • Fuel lines from the fuel pump
     
4. Raise the fuel pump from the tank.
   
5. Remove the fuel filter assembly.
   

To install:

1. Install or connect the following:
   
   • Fuel filter to the fuel pump. Lower the pump assembly into position
     
   • Fuel lines
     
   • Negative battery cable
     
2. Start the vehicle, check for leaks and repair if necessary.
   
3. Install the fuel pump cover plate.
   

Inline Filter

1. Before servicing the vehicle, refer to the precautions in the beginning of this section.
   
2. Properly relieve the fuel system pressure.
   
3. Remove or disconnect the following:
   
   • Negative battery cable
     

Exploded view of an in line fuel filter and related components

Air intake hose and/or filter housing, if necessary

Fuel line clamps, if equipped

Fuel lines from the filter and plug the openings

Filter clamp bolt/nut by loosening them.

Fuel filter from its mounting bracket

NOTE Note the direction of the flow arrow on the filter so the replacement filter can be installed in the correct position.


To install:

1. Install or connect the following:
   
   • Fuel filter in its mounting bracket, making sure the flow arrow is pointing in the proper direction
     
   • Fuel lines to the fuel filter
     
   • Fuel line clamps, if equipped
     
   • Air intake hose and/or filter housing, if removed
     
   • Negative battery cable
     
2. Pressurize the fuel system and check all connections for leaks.
   

have you checked fuel pump presure to see if it has fuel to the rail,
if no fuel in the rail,
check fuel pump relay-and fuses,
last would be to replace fuel pump

Disconnect your supply lines to the cylinders. Try starting the car while someone watches the disconnected lines. If fuel pumps from the lines you need to have your injectors cleaned or replaced. More likely it is your fuel pump that has gone bad. If you dont see any fuel flowing from the disconnected fuel lines, try replacing your fuel pump and replace your fuel filter too just to be prevent pushing any dirt and sediment from a dirty filter into a new pump.

check fuel pump relay, you should hear a click when you turn the key to on, you should hear a whirling sound in gas tank when key is turned on

If the car stalling then the owner of the car should check on the fuel pump assembly. prepare the tools and equipment in servicing the fuel pump,the fuel lines and the fuel filters.In the fuel pump you have to locate the fuel pump,disconnect fuel lines from the fuel pump,remove fuel pump from the engine,dis-assemble fuel pump, check the diaphram for defect , replace defective parts,assemble and install the fuel pump.
In checking the fuel lines : prepare the tools or equipment in servicing the fuel lines .So that the fuel will flow freely and no abstraction within the fuel lines.locate the the fuel lines ,visual inspection on dual line for leakage, disconnect lines at fuel pump and fuel tank .use compress air to remove sediment on fuel lines,re-install fuel lines to the unit.
the fuel filters :prepare the equipment or tools in checking the fuel filters that is going to be used.So that when fuel filters is removed ,no fuel will spill on the vehicle and no parts are lost or broken.Locate fuel filter,disconnect lines at fuel filter ,observe safety practices ,If the fuel filter is dirty then you have to clean it but if it is worn out and not anymore to be used then install new fuel filter.

before you drop tank again, check fuses & relay.then disconnect fuel line @ filter turn key to on position should hear fuel pump run and get gas stream out of line. if no flow from line new pump faulty be sure & remove negative battery cable first good luck.