Fuel pressure question

[sljs3413]

I posted a issue a few days ago about my z not running right and to the point where it boggs down and wont drive in gear. Well i tested the fuel pressure today and im even more confused. With the tester hooked up and key on i get maybe 5psi. When i turn the engine on it slowly moves up to 47-48 psi and if i throttle it up it goes to 50. When i turn it off it drops back down to 25-30. Pumps? Filter? Both?

[TX '90 ZR1]

Originally Posted by sljs3413

I posted a issue a few days ago about my z not running right and to the point where it boggs down and wont drive in gear. Well i tested the fuel pressure today and im even more confused. With the tester hooked up and key on i get maybe 5psi. When i turn the engine on it slowly moves up to 47-48 psi and if i throttle it up it goes to 50. When i turn it off it drops back down to 25-30. Pumps? Filter? Both?

None of those numbers sound right.
When you turn on the key you should get about 42 lbs. Should hold there or close. (The pumps just run a couple of seconds after turning on the key)
After start up the idle pressure should be low 40's and increasing to low 50's at full throttle.
After shut down, pressure should hold about 42. Some will settle a bit, but not bleed totally off if everything is correct.
If the filter has not been changed, I'd do that first just because it is easy and needs to be done anyway.
After that, start isolating systems to find where the issue is.
The FSM has some pretty good troubleshooting ideas on the fuel system. There is also a lot of information on this issue here in the forum archives.

[onetinsoldier]

Definitely replace the filter first ! Then test it ! Fuel line clogs can be filters , fuel sock or any other type of screen .
I have seen the socks deteriorate and debris plug the pump , the lines up to the filter . Once you have the filter off , connect a rubber hose to the tank side , put the other end in a container and run the pump , just to clear the line .Look for debris !
Also drain the filter to see if anything backwashes out . Give it the blow test too !