Lauren,
You need to post that over at the Isuzu P'up site, too (
http://www.isuzupup.com). We even have another member it Pittsboro, NC who can probably help you!
I think if you can get an uninterrupted supply of fuel to the pump, the pump will take it to the motor. I've never had to loosen my fuel lines to the injectors, but I do still have the stock filter. Pee Roy is right, an inline pump will work. But I can understand not wanting to buy and install one, they're close to $50. Do you have an air compressor?
Jack
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'83 Isuzu P'up Diesel LS - Original Owner
JoeIsuzu@IsuzuPup.comIsuzuPup.com