Fuel pressure Regulator – return line

[steve]

Hello Readers,
Have couple of Qs on fuel on pressure regulator.

1) At the time of prime(key on engine off), should there be any fuel be coming out from the return port of the pressure regulator?

2) After 20 mins of drive and the engine is turned off, should there be any fuel be coming out from the return port of the pressure regulator immediately after key is turned off?

Attachments:

• return_fuel_line.jpg

Topic

[John Hugon]

In the picture the arrow appears to be pointing to a vacuum line for engine load to fuel pressure regulator. If you have fuel coming from that port the fuel pressure regulator is defective.

aguy01 stated:
1) At the time of prime(key on engine off), should there be any fuel be coming out from the return port of the pressure regulator?

NO…No fuel should not be coming out from the return port
aguy01 stated:

2) After 20 mins of drive and the engine is turned off, should there be any fuel be coming out from the return port of the pressure regulator immediately after key is turned off?

NO…No fuel should not be coming out from the return port
Engine not running turn ignition key on-prime
1) Engine not running /with a fuel pressure gauge installed, turn the key on and the fuel pressure should go to manufacture specs almost instantly, then in about two to five seconds the fuel pump turns off, the gauge will drop to roughly 5psi in the span of 7-10 seconds and no fuel in the return line.
Engine shut down
2) Engine shut down no vacuum to fuel pressure regulator no fuel should return to fuel tank.

[EricTheCarGuy]

By the picture I can see you have a Honda. Forget about the fuel system if you’re having a performance issue. BTW, there will always bee some fuel coming out of the regulator return. Honda’s rarely have fuel delivery problems and I advise people to look elsewhere if they’re experiencing a performance issue on a Honda.

Perhaps a better question would be are you experiencing a performance issue with the vehicle? Then take things from there. If you are experiencing a problem, I would suggest you read through this article I wrote.

http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[John Hugon]

EricTheCarGuy stated:
BTW, there will always bee some fuel coming out of the regulator return

I have to agree to disagree with Eric on this one. First thing; I never worked on a Honda and I don’t know their system. Second thing; I never checked a fuel pressure regulator to see if fuel was returning back through a return line in the real world of diagnosis with engine not running. In my training under GM and Ford we never checked fuel pressure regulators that way and I never had to. With all that said, and no one answered auy01 post after a few hours I give it my best effort and checked a GM Tech magazine I still have about fuel pressure regulators and this is why I wrote what I did:

Written in the article:

Caution: When removing the fuel pressure regulator vacuum tube or blocking the fuel pressure return port will spike pressure to the fuel pump’s maximum pressure, normally at or above 100 PSI causing the fuel pump relief poppet spring to open the bypass at the fuel pump base or the fuel pump may be permanently damaged. GM OEM fuel pressure regulators must hold pressure for 30-minutes when engine is shut-down to pass EPA emissions standards; at this time no fuel will pass through the fuel pressure regulator with engine not running.

After being a moderator on an auto factory web site for a period of time; one thing that always upset me was; people writing things that were wrong and misleading diagnosis. auy01, my apology for misleading you. Eric being the professional as he is; would not have stated what he said without seeing it.

The next time I get a chance to work on a car/truck, which isn’t very often(I’m retired) I’ll check a fuel return style fuel injection system in real life and post the results that I find….that’s if I don’t spill fuel on the engine and start a fire…

[Author]

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