fuel pump question

99 jimmy 4.3 L-220,00 k
Have an intermittent bogging problem when truck reaches operating temp..
new ignition parts,new fuel filter etc. starts and idles fine.
Suspecting fuel pump as culprit, done ptessure test with igntion on :15 psi, start vehicle fuel pressure takes about 15 seconds to reach 56 psi. I hear the fuel pump whine over for 2 sec. when ignition turned on but lousy pressure at rail.
My Question: Is it possible that the fuel pump power source is coming from the oil pressure fuel pump sender instead of the relay because it takes so long to bulid up or is the pump shot?

My fuel pressure is up in a second. You might try replaceing the fuel filter first.

I have already replaced fuel filter. Done a second pressure test today before changing pump and the pressure did go up to specs. in just a second. I am witts end with this truck. Had it to 3 different mechanics, including a reputable transmission shop and they have no idea whats going on. The problem is intermittent which makes it hard to diagnosis.

99 jimmy 4.3 L-220,00 k
Have an intermittent bogging problem when truck reaches operating temp..
. . . . is the pump shot?
Exactly what do you mean by bogging? Please explain in more detail.

Not likely your fuel pump. More likely it's one of the sensors on the engine, or the fuel pressure regulator.

What kind of a reading do you get after bleed down on the fuel pressure test?