1997 xlt extra cab 5spd 2wd 4.0 sluggish

[Rick W]

Oh wise ones…

I need a step-by-step to pressure check my fuel rail and components, please and thanks. ‘97 4.0 5sp

Remember, the truck runs fine at idle and with a light gas pedal, but if I step down hard on the gas, it loses power and it sounds like it’s either starved for gas or starved for air. It has a new air filter. This was all after I put in some carbiclean/sea foam to clean out the fuel system.

I have a new fuel tank assembly, a new fuel rail pressure regulator, and I have new injectors and the upper intake gaskets and such. I also bought the injection pressure testing system from harbor freight.

Questions: I know how to hook up the pressure tester to the fuel rail. Do I just key the pump a couple times or do I actually start the truck to check the fuel rail pressure?

If I rev it with the truck running (is that safe?) and the fuel pressure drops, I’m assuming I’m going to change the regulator first (easy) and then test it again

If that doesn’t solve the problem, I’m assuming I have to change the fuel tank pump assembly. I have to undo all my wiring, pull the toolbox, extra battery, fill neck, etc. to get to it.

If neither of those corrects the problem, the next step the upper intake has to come off to change the injectors?

Yes/no? Any tips or procedure advice would be greatly appreciated.

 

[scotts90ranger]

The fuel pressure regulator is vacuum referenced, I don't remember the fuel pressures it is supposed to be but I think it's around 40psi at key up or running with the vacuum line removed, it'll likely go down just under 10psi at idle if my quick guesstimate is reasonable... as load increases fuel pressure increases (for your mind to make sense of it, it's to try to get the differential pressure across the injector the same at all conditions...). Yes it's safe to drive with the gauge on and if it is the problem you would lose pressure when under more load so it would likely take a test drive to rule out the pump. If the pressure is right at all the regulator is working but if it goes down under power then the pump can't keep up.

 

[Rick W]

The fuel pressure regulator is vacuum referenced, I don't remember the fuel pressures it is supposed to be but I think it's around 40psi at key up or running with the vacuum line removed, it'll likely go down just under 10psi at idle if my quick guesstimate is reasonable... as load increases fuel pressure increases (for your mind to make sense of it, it's to try to get the differential pressure across the injector the same at all conditions...). Yes it's safe to drive with the gauge on and if it is the problem you would lose pressure when under more load so it would likely take a test drive to rule out the pump. If the pressure is right at all the regulator is working but if it goes down under power then the pump can't keep up.

THANK YOU!

Could it be the vacuum line to the regulator? I’ll check that first.