Questions about... 1987 F150, 302, dual tanks and what appears to be a fuel system related problem.

Some items.
Wont run now but ran well when shut down.
Good spark at coil and plugs, Good fuel filter.
Will start and run breifly.. maybe 3 - 5 seconds on its own. Will start and run briefly if using starting fluid. doesnt backfire when trying to run, or in spinning over....So, not a timing chain issue.
Checked power to inline fuel pressure pump.... on rail between forward tank and fuel filter -- none.
Running a jumper wire from the NEG battery terminal to the pigtail just behind the air cleaner housing, I can get the pump to run and the engine to start and run fine...but the pump stays engaged. So I know it is not the relay or fuze link. When pulling the jumper wire out of the pigtail the engine quits in a couple of seconds.

Any suggestions on what else I might try next, or what the problem might be?

Thanks.

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