fuel delivery help

[rcr244]

87 ranger. 2.9l v6. found out i had a bad intank fuel pump. went to a wrecking yard and got a 89 sending unit and took the pump off of it and put it on my 87 sending unit. i put everything back together and found out that 89s only have one fuel pump. im wondering if this is the reason why im getting low pressure to my schrader valve after i drive for a while. the truck is gutless and the engine bucks. both fuel pumps are working. changed the fuel pressure regulator and front fuel filter. i took apart the plastic canister and that filter seems to not be clogged. any help would be nice.

 

[Bronco_Chuck]

I would try bypassing the high pressure pump on the frame rail. My guess is that the pump is worn out and no longer creates the pressure you need, but at the same time wont let the fuel flow freely from the in tank high pressure pump.