4.5 V8 fuel pressure regulator

[copilot]

I've had my car for six months now (not without it's problems) but the engine has been fine (up until this week end...see other thread). I have noticed that there is no fuel return pipe on the fuel pressure regulator. Does anyone know why? If you have a 1999 4.5 does yours have a return pipe? Why has it been runnung fine without one?

[davidn]

I always thought that was for a vacuum pipe, not fuel return. Apparently this engine doesn't need that, although questions have been asked in the past if one should/could be fitted.
HTH.
David

[copilot]

Makes sense, but what threw me was this article.
www.emeraldm3d.com/ems.htm#injectionschema

[davidn]

Yep, that's confusing. Someone who knows what they're on about will be along soon.
David

[mars]

The fuel rail has an in and an out. The FPR has a little nozzle on top which is a vacuum take-off which *can* be used to increase fuel pressure as you press the pedal. It would sort of act the same way as a Webber used to have an accelerator pump to add a dash of extra fuel during sharp throttle openings, to stop the engine going lean for a rotation. Anyway, there's no need for the FPR to perform this function with a fully mappable ECU (as you have) so it's left open.

But trust me, you *do* have a return pipe.

[mars]

That Emerald diagram is misleading as the fuel return appears to come off the top of the FPR when in fact it comes off the fuel rail itself and the nozzle on the top of the FPR is a vacuum take-off.

[copilot]

Thanks again, there's always someone who knows. Well done!

If you are still there MARS can you help with my other thread re half of the engine not receiving fuel when being reved?

Edited by copilot on Monday 23 April 19:15

[mars]

I'll go and have a look...