possible fuel pump going

[redneckchevy90]

so this is really buggin me I have a 90 with the 350. when I fill up the truck runs great. but as soon as I burn a 1/4 tank the thing sounds like diesel truck when put under load very loud knocking noise.I can put it in park raise the rpms to about 15-1800 no knock but as soon as I put it into gear it starts the knocking again. am I looking at a fuel pump going out.

 

[jarede525]

Put it in neutral and rev it. If it slows way down or won't go past around 3 or 4 thousand rpm, it's the fuel pump. At least that's how I realized mine was going out..

And sooner or later it just won't be able to build up the pressure to start at all...

 

[redneckchevy90]

I'll try that tomorrow when I get to work

 

[frito-bandito]

See if the pump is running louder than usual too.

 

[GMCTRUCKS]

If it's from 1990 replace it with a Delphi brand not no cheap one from Auto Zone.

 

[frito-bandito]

Good point

 

[redneckchevy90]

forgive me for asking a stupid question. if it is my pump would it be causing the the motor to knock like crazy.

 

[frito-bandito]

That don't sound good man.

 

[redneckchevy90]

the weird part is it only knocks once I burn over 1/4 tank of gas from full

 

[redneckchevy90]

so I've figured out my pump is going out. so my question is should I get just the pump or the entire assembly.