fuel pump problem 1991

I need help with a 1991 chevy 2500 series 5.7 litre. I have no power to the fuel pump. I wired in a toggle swith and put 12 volts to the grey wire to the fuel pump fuse and it would run but with no high idle. Now it wont run
again, no power to the fuel pump. any help would be greatly appreciated.
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Checked or changed the relay? Checked the fuse.

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What would run, the pump or the engine?
Are you jumping the pump through the load side of the fuse? If so, are you also powering the line side from the PCM?
skimmer

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I am jumping the fuse opposite of the load side. when i first jumped power to the fuse the engine would start and run, but with no high idle. it worked this way for about a year. I just use it now on my farm. but now it wont run again with no power to the fuel pump. nothing was changed in the wiring. already tested the relay and oil pressure switch. thank you very much for responding.
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Have you tested the fuel pump flow and pressure?
or amps pulled through an ammeter jumped to that fuse with the key off?

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