Fuel pressure regulator

I pulled the fuel pressure regulator off the dead engine I got a while ago and thought I would check it over. I could not push air through it (hooked it up to a bike pump with a gauge). I soaked it with an oil spray for a few days, still no luck. Next I tried a small pin punch down the inlet hole and give it a few light taps. Still not luck.
I kept trying progressively harder and it would not free up (I got up to 180psi with the bike pump!)

I figured it was not worth persevering with, so opened it up. See the picutres if you want to know what is inside one. I was expecting it all rusted up, but other than some caked up sediment it was quite clean in there, and the diaphragm seemed intact.

The spring is on the vacuum connection side, on the opposite side the outlet tube sits against the small disc in the center of the diaphragm.
This sets the pressure in the fuel rail. As engine vacuum increases it lowers the pressure in the fuel rail, so reduces the fuel going to the engine.
Richard .

Thanks for sharing Richard.

So why do you think it was not working?

Jammed up or not enough pressure from the pump you were using?

I have a spare one of these off a previously working but rod knock engine and wondered how to suitable test it.

I do not know how long it had been sitting and left open, and possibly left outside for a while. I expect dirt build up and corrosion. Not an issue on pressure as I hooked it up to a bike pump, so applied much more pressure than the pump could supply.

Best way to test if you have a fuel pump is rig up to the fuel pump with a pressure gauge and check it to factory specs. Ideally if you can apply vacuum to the vacuum line also and check the pressure variation.
Not that I have seen a failed one, but I expect old work out ones would either not hold the correct/stable pressure or the diaphragm would leak.
It would also be good to check how long it holds pressure when you turn the pump off. It should hold pressure for a long time if everything is good.


My test has always been if an engine runs well with it.

Seeing mine did and I have stuck it in a plastic snap-lock sandwich bag since, it should still be good.

Hopefully I never need it…