Check Valve question?
 

Apologies for the dumb question, but what's a check valve used for on a Fuel Pressure Regulator and how does one test it to verify it's working properly?

Anyone got a pic of what one looks like?

CIS check valve is used to maintain fuel pressure in the system after engine is shut off. Usually if the valve is bad, you'll have a hard start if the car sits for several days. There's also a check valve in the fuel pump.

You'll need a fuel pressure gauge that should be used as a leak-down.

Sorry, no pic...just memory,

So, if I shut down the engine, the check valve on the regulator should maintain a fuel pressure at the rail equal to the fuel pressure at idle?

Is the check valve a separate component to the fuel pressure regulator, or is it built in?

I have a fuel pressure gauge on my left fuel rail and it shows approx 4-5psi when the engine is shut down. Does that mean my check valve is faulty?

The "check valve" is on the output side of the fuel pump. Does your car have to be turned over a few times before it starts? That is a common symptom. That is pretty low residual fuel pressure, which does point to a plugged check valve. They are cheap and easy to change.

Cheers

Sorry guys, I was mistaken. The fuel pressure only drops to 4-5psi a few hours after shut down. When first shut down, the fuel pressure still registers ~43psi, which I KNOW is too high anyway, but at least I know the check valve is OK.

I guess my project this weekend is to remove all the vacuum connections to the FPR, check that they are all not blocked and re-install them. I suspect either my FPR is screwed and not regulating properly, or it's not getting a good vacuum signal from the intake.

After my fuel damper ruptured and bled excess fuel into the vacuum lines, it's possible residual fuel (or gunk) is stuck in my vacuum lines, blocking the vacuum signal to the FPR :confused:

43psi at idle is just WAY OVER the top!

Wyd-If your damper ruptured, then fuel likely got into the fpr, and it is either sticking it open or has it fubar'd?

In any event, I doubt that the vaccum/boost port of the fpr likes to see gasoline.

Yup, I agree Greg. Might try removing the FPR and disassembling it to see what's gone wrong inside. It's the custom Protomotive one, which I believe can be serviced internally with new diaphragm etc...

No wonder my wrench couldn't adjust my CO lower than 4.9%... the fuel pressure is just too high and is resulting in an overly rich mixture :mad: