FUEL DELIVERY

The pump loses power or the engine loses power? Sounds like a loose connection in the wiring if the pump is losing power. Check your mercury switch and make sure it's secure and upright.

If the spot welds that secure the baffle in the bottom of the tank break, the baffle will move and allow the fuel to slosh away from the pump pickup.

There is no mercury switch in the fuel pump electrical system. There is an inertia switch that shuts the pump power off if the car is hit in a collision

If the pump loses electrical power while the engine is running, it will set a code. Dump the codes and see what the computer says is wrong.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is about $30 or so at AutoZone or Walmart.

Or for a nicer scanner see http://www.midwayautosupply.com/detailedproductdescription.asp?3829 – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $35.