Verifying clean power is what Rusty is getting at. That has two components:

Minimum voltage uder load at the positive lead going into the pump

Minimum ground lift at the ground lead going into the pump.

The pump doesn't know anything about batteries, alternators, wire resistance, etc. It only knows what the voltage is BETWEEN the two leads at the pump. If the ground attachment to the frame is poor then there will be a voltage drop across that resistance and the negative/black voltage will not be near zero under a load, there could be a drop of multiple volts while maximum current is flowing, effectively "lifting" the ground. There are two ways to verify proper operation. One is to test the positive lead under a load and be certain that you are near battery voltage and then measure the resistance from the black lead to a good clean point on the chassis to verify low resistance. This would imply proper net voltage to the pump. The other way is to measure the voltage across the leads right at the pump under a load. If its not within a volt or so of the voltage at the battery posts under that same load then you figure out if the problem is in the positive circuit or the ground connection. A test light will not help you on the ground connection to the frame. We already know that there is a useable connection because the pump turns on but what we don't know is if the pump sees a healthy net voltage at the pump leads while running. If the ground connection is marginal or any of the wiring was done half assed then as the pump runs the voltage might be dropping to an unsafe level and the pump may see a "brown out" condition and shut down or eventually burn up. Replacing pumps under such a condition could be just an endless cycle.

George

 

With regards to your question about if it has to be the pump, I don't know of any other explanation unless if the pump was replaced as parts and not an entire unit. That said, I have never dealt with this before so perhaps one of the other guys can chime in.

George

 

Yes, good pump assemblies hold pressure. The 3/8 fuel supply line is the largest of the 4 in the group that run along the top of the frame. Something could have kinked it or otherwise resticted the flow and smoked the pump. Follow that and make sure it's in good condition. Connect the black wire of your volt/ohm meter to the frame. On ohm setting touch the red wire on the meter to the pins connected to black wires in the plugs. It should read 5 ohms or less. Leave the black wire on the frame and turn the key to run. Set the meter to dc and touch the positive pin for the fuel pump. That should be within 10% of the battery voltage. The only other wierd thing involved is me.

 

 

 

Follow the solid black line. That's too much resistance.

 

I haven't know that the pump should keep the pressure when it's off for at least for 10 mins. But.. if the pump that is off (=unpowered) and doesn't hold pressure it has nothing to do with electricity. Following an electrical wiring sounds like unnecessary, misleading job.
EDIT: Oh, I just got Your idea. A check for a brown-out condition. You may hook up the probes to a pump terminal and check what voltage You have while in operation.