Hi Phil,

Thank you for your kind words. I did not intend for Joe, the OP, to think I believe his fuel pressure regulator has failed, but instead wanted to add an example from my experience to demonstrate your thoughts warning about this less common mode of failure.

The usual way the FPR fails is the diaphragm becomes porous. I've taken them apart once this has happened to see what the rubber looked like. The diaphragm is made from two sheets of elastomer, and my observation is the one facing the fuel is the layer to lose its resilience. I blame that on ethanol, just as I credit the ethanol for removing rusted springs (regulator and pump check valve) as a failure mode. I'm no expert in this chemical compatibility, just spouting opinions formed from what this additive does to small engine fuel systems.

That "soldering iron" is just an ordinary nail set ground to imitate a chisel. I was using it to lift the rolled cylinder capturing the valve disc and spring. The valve disc is fixed to the ball, and I believe the shape of the retaining plate (reminiscent of the blower squirrel cage impeller retainer) is exactly for the purpose you say it is. Of course, Houdini the Spring, found one of those openings made for assembling the ball/disc into the well with its rolled ridge. When this is assembled (as in this working valve from a porous regulator) the disc has maybe 15 thou travel against the small spring.

The valve seat is polished, and as the witness mark on the disc shows, controlling the alignment of the seat and disc is the centering job of the rubber diaphragm. This is more evidence that the life of this device is almost wholly wrapped up in the performance of this rubber part.

That the regulator costs more shouldn't be a surprise to me, given its manufacturing precision required in low, aftermarket replacement part quantities. Adjustable fuel regulators are used by tuners and racers, and I think modern cars have begun to use pressure sensors and feedback to turbine pumps rather than these brute force spring-loaded regulators returning fuel to the tank.

Here's what the valve seat looked like on that stuck regulator. You can see the outlet fitting (and inlet fitting) is pressed into the housing. The valve seat looks worn as if the diaphragm was weak on some point of the clock.



The following photos are of a working valve (small spring where it belongs) taken out of service for leaking too much fuel into the vacuum chamber.







And finally, Mr. Cheap thought he could buy a used regulator from a seller who, I guess roams the California yards for them, selling them as "tested" units. I can only imagine how he tests them. Return and refund was no problem at all. I only wish the seller didn't need me to send it back; that this photo would have been enough for him, so I could dissect it and see how gross the rip in the diaphragm became to run this stream out the vacuum port! In this case, the curiosity wasn't worth $40.


--
Art Benstein near Baltimore

Never miss a good chance to shut up.