[1hot.ss]

hello! I just had a dual pump system installed in my car noticed once it was installed the gauge on the fuel pressure regulator does not read and the needle just flicks around. I noticed that there seems to be a line that needs be hooked up to a vaccum line but my mechanic says that is only for port injection cars he says the gauge is wrong? Just want a second opinion

[1hot.ss]

Link to picture for reference

https://files.fm/u/2gh3s5y4ja

[easttxss]

The port is for boost reference. It will add 1 pound of fuel pressure with every pound of boost on a Forced Induction car. Doesn't do anything on an N/A car.

[1hot.ss]

oh so i do need it then? I have a blower on my car maybe that is why my car was running out of fuel at the rail on the dyno…

[GreyGhost702]

You might get better feedback in the tech section of the forum.

Might need some more context for this, as well. Why the need for a regulator on the low side? So you went dual in-tank pumps, looks like upgraded line. Are you doing a return style fuel system? If not, there shouldn't be a need for a regulator in a returnless system. The regulator will cause the computer to fight it, because the computer controls the pumps. It spins the pumps via voltage controller, which controls low-side pressure as commanded. This may be why the gauge is showing erratic readings, it's trying to fight the regulator for pressure control.

Again, just need more info on what is going on here. easttxss is also correct, for the boost reference port. Though, the port would likely see vacuum depending on the sample source, I don't think it would hurt either way to hook it up. That gauge, however, is only sampling what's happening in the valve body, the gauge won't see vacuum or boost, only the pressure in the fuel line. If the needle is flying, so is your fuel pressure most likely.

[GreyGhost702]

Originally Posted by 1hot.ss

oh so i do need it then? I have a blower on my car maybe that is why my car was running out of fuel at the rail on the dyno…

If you're running out of fuel at the rail, and are running a return style setup, and the pumps are spanked, it ~could~ be a bad regulator, or the pumps are just whooped. Can always step up to bigger dual pumps or a tripple pump. And/or voltage booster. The gauge jumping all over could be a sign of trouble for the pumps, as well. A loose connection in either the fuel lines in the tank, or perhaps even electrical (though I feel any faulty electrical in regards to the pumps would be seen by the FPCM and likely throw a code. Still a guess, without knowing the details of your car and how it's set up.

If you're running out of fuel at the rail, and are running a returnless style setup, I stand by my original post, of why do you have a regulator on a returnless setup?

[SomeGeoffGuy]

Not sure the few pounds you would add under boost even matter for the low pressure side as long as it can support the volume required to the high pressure side. Interesting question though!

-Geoff

[Joshinator99]

Originally Posted by 1hot.ss

hello! I just had a dual pump system installed in my car noticed once it was installed the gauge on the fuel pressure regulator does not read and the needle just flicks around. I noticed that there seems to be a line that needs be hooked up to a vaccum line but my mechanic says that is only for port injection cars he says the gauge is wrong? Just want a second opinion

If you’re DI only, a vacuum line is not needed.

If you have DI and PI (added TooHighPSI port injection system or equal) then you don’t need the vacuum line either as long as your fuel pressure is still 45 psi or so AFTER backing out the max boost pressure. So, for example, if you command 65 psi under boost and are running 15 pounds of boost, you’d still have 50 psi to the port injectors so you are fine.