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Discussion Starter #1
Well I've been trying to figure out my fueling issue on my stock 6.0 with twins, holley efi controlled

Holley 12-1400 pump (both wired on all the time. 2 relays)
Magna fuel 9950 regulator
-10 feed to dual -8 at the back of rails
Regulator after rails.
-8 return to the tank

The problem I'm having is as it starts making boost the fuel pressure falls off instead of rising. Have the vac port on the reg after the throttle body.

Also at 43psi is fuel suppose to constantly be returning to the tank? I know it does if I lower the pressure. It barely returns anything with engine off and pumps running.

Any ideas?
 

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Sounds like pump is junk. With pump running and engine off will it keep picking up pressure as regulator is adjusted?? If it won't make 43psi + max boost pressure, it's junk. As an example I run 75psi base + 40psi boost =115psi that pump has to be capable of producing. Hope this helps.
 

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I think I would plumb the regulator reference pressure to before the throttle body...?
No. The object of the pressure reference port is to keep the same net pressure across the injector for consistent fuel metering. Putting pressure reference on turbo side of TB will cause major fueling issues.
 

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Discussion Starter #9 (Edited)
I'm thinking it's the pump being it use to be quiet and now it's loud making a dumb noise. It's 3 years old.

The voltage when it starts to fall off is 13.2v

If I crank the regulator all the way down it won't make more than 50psi no matter how far I turn it.

I'll send the pump off and see what holley says
 
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