Checking a fuel pressure regulator that is out of the car

Question

I happen to have a fuel pressure regulator of a petrol car lying around left by the previous owner and suspect that it might be still good, since the previous owner was just changing parts randomly hoping to fix a certain problem. How would one check if the regulator is still good for use?

As I understand the main cause of FPR failure is a ruptured diaphragm inside the metal casing that separates vacuum side from fuel side causing petrol leakage into the vacuum pipe. Does that mean if I blow on the vacuum inlet and no air leaks through - the membrane is still good?

Answer 1

The best (read: easiest) method to check this is doing it on vehicle. In that case, you put a fuel pressure gauge on the engine at the Schraeder valve (if so equipped) and check the fuel pressure at idle and ensure you have the proper pressure. Then pull the vacuum line to and check the pressure again, which should have changed (it should go up between 5-7 psi). Another check on engine is to see if there is fuel coming out of the vacuum port. If so, it's bad.

While the diaphragm is the most common failure, you could also have a valve failure or a spring failure as well. I don't believe you can check for these off of the car, unless you have specialized test equipment. You may be able to do it by using hand held vacuum pump and see if the diaphragm will hold a vacuum. The tool looks something like this: