Fuel pressure question

[Magikal]

Recently installed a 7.4 vortec in my k5. Starts and runs well although it hasn't been test driven yet. I checked the fuel pressure at the rail and it's right at 50psi running. Seems like I read somewhere that I should have 60+....is this a problem that should be addressed or should i just run with it as is??

 

[dyeager535]

Recently installed a 7.4 vortec in my k5. Starts and runs well although it hasn't been test driven yet. I checked the fuel pressure at the rail and it's right at 50psi running. Seems like I read somewhere that I should have 60+....is this a problem that should be addressed or should i just run with it as is??

That does seem low, I am sure I've heard it stated on here multiple times that the later Vortec motors require 60PSI, and the EP381 Delco pump is what is used for that application.

Is it a new pump? Adjustable regulator by any chance?

 

[sweetk30]

some applications very the pump voltage or pressure regulator when not under load .

but 50psi does seem a tad low .

bring your rpm up to 1500-2000 range and watch it then .

 

[bigblock72]

some applications very the pump voltage or pressure regulator when not under load .

but 50psi does seem a tad low .

bring your rpm up to 1500-2000 range and watch it then .

What is it with the engine off? May need to jumper the fuel pump relay to test it properly as the spec is 58-62 with the engine NOT running.
The fuel pressure regulator is vacuum referenced and will drop the fuel pressure 6ish psi with engine running with no load.

 

[Magikal]

Today I did as suggested and checked pressure with motor running. At idle it was steady 49psi. After shutting it off and waiting 20+ min it had only dropped to 45psi. Hmmmm........??

 

[dyeager535]

Today I did as suggested and checked pressure with motor running. At idle it was steady 49psi. After shutting it off and waiting 20+ min it had only dropped to 45psi. Hmmmm........??

I don't think the residual pressure is very meaningful. If the hose in-tank is broken (if this setup even has one) pressure will drop to zero in no time flat.

Did you test as stated, jumpering the relay? That's where you'd know if it's 58 or not.

 

[Magikal]

No, didn't jump relay.

 

[dyeager535]

If the FPR adjusts pressure via vacuum, that would make sense to test that way. Assuming the pump was good, pressure will be what the regulator is set for, not what it is when vacuum referenced.