Are Fuel Pressure Regulators Supposed To Hiss?

[Sy_ 0]

As the title says really.....this' on a '93 1.9GTi

 

Any help appreciated.

 

Cheers,

 

 

Sy

[miamistu 1]

I hope so. My one does - quite loudly!

[Sy_ 0]

Mine too, just wondering if it was related to why she wouldn't start this morning!

[205007 12]

mine does too

 

but im sure thats a bad sign?

[welshpug 1,657]

nope, just means its working to maintain the correct pressure, more audible at idle as the demand to the injectors is lower and more fuel is flowing back top the tank, via the regulator.

[miamistu 1]

But then the fuel pressure's lower at idle so that should make it quieter surely?

[Dream Weaver 2]

I would've thought the pressure is maintained at 3 bar whether at idle or WOT, otherwise you would have a funny bouncing idle.

[welshpug 1,657]

not quite, notice the little pipe that goes to the inlet manifold? works a bit like vac advance.

[M3Evo 0]

The fuel pressure is maintained at 3bar ABOVE MANIFOLD PRESSURE so with the throttle shut and the engine drawing 1/2bar of vacuum (or 15" of mercury or whatever the proper units are) the fuel pressure will be 2.5bar (gauge pressure) which rises up to 3bar (gauge) at WOT when there's pretty much atmospheric pressure in the manifold

 

Handily enough, if you apply positive pressure to the FPR, the fuel pressure continues to rise correspondingly so if there's 1bar of boost in the manifold, the fuel pressure will be 4bar gauge.

[kyunis 0]

Hi. Mine makes more of a squeeling noise! Prob coz im running it with twin carbs. Whats the cure? would a power boost valve help ? Thanks

[M3Evo 0]

If you've got carbs and a pump suitable for carbs (so not the injection pump and a funny pressure reg) a "Power Boost Valve" won't do anything as the float chambers in the carbs should do their own regulating.

 

Similarly, I can't see how a Power Boost Valve would boost the power on an injection engine either!

[kyunis 0]

Thanks for the reply , whats the best setup if using carbs? what do i use? Thanks

[M3Evo 0]

Think the proper way would be to replace the injection pump with one that supplies 5psi or so of fuel pressure and then let the float chambers take care of the rest.