Fuel Pressure question

[edfiero1]

TBI Engine is running lean. I suspect a fuel problem. Already swapped out injectors with known good ones, no change.
Measured pressure on the low side at 9, but it's steady.

When pinching the fuel return line, what behavior would point to a pump problem vs, what is a regulator problem?

I've seen people say that if the pressure doesnt rise with the line pinched then the pump is bad. While others say that if the pressure rises this is a regulator problem because the spring isn't able to control the pressure.

Which is it?

[fastacton]

If you pinch the return line and the pressure doesn't rise it is a pump problem. How would a regulator be able to keep the pressure low if it doesn't have a place to relieve the pressure (unless fuel is spilling out everywhere)?

[edfiero1]

If you pinch the return line and the pressure doesn't rise it is a pump problem. How would a regulator be able to keep the pressure low if it doesn't have a place to relieve the pressure (unless fuel is spilling out everywhere)?

Thanks Makes sense.
How would you diagnosis a bad regulator?

[fastacton]

Normally it'll be easy because fuel is spilling everywhere. These regulators are very simple, it's just a spring and a diaphragm which works as a bypass valve and there really isn't anything to fail. If it was working properly, it should stay that way until the diaphragm fails and a leak happens or the spring rusts enough to lose it's tension. The only problems I've ever seen are leaks, anything else is a pump or line problem.

[dispoejoe95]

Not all that common but I have heard a regulator spring can break or just get weak and not hold pressure. What was your pressure before?