Unfortunately cheap aftermarket parts often times adds to the problem. Hopefully it doesn't bite you.

You are ahead of the game now that you have a fuel pressure monitor. You definitely have low pressure. To avoid random parts replacement, you need to do the leg work unfortunately. Usually the low pressures are due to one of four things : 1. bad fuel that gels or has excessive water content, etc. 2. Lack of maintenance or using improper filters or excessive filter change intervals 3, weak fuel pressure regulator spring 4. weak pump.

That said, it could be a leak in the system letting air in, could be a kink in the fuel line, could be sediment in the tank, etc.

It is a pain, but troubleshooting procedures call for taking suction and discharge pressures to eliminate the plugging or leak issues. The average owner is not set up for this unfortunately. If not already done, the fuel pressure regulator should be updated. Take care, sometimes the installation isn't done correctly and it causes the low pressure issues it was intended to prevent. If that isn't an issue, fuel quality and filters are good, the suction isn't restricted, and the pump discharge pressure itself is still low, then it is likely to be the pump.

 

I hear ya. Replacing the fuel pump seems like a pretty quick job, so my thinking was buy a cheap new fuel pump, replace it, and check fuel pressure again. If the pressure is still low then I'm only out $50 and I'll move on down the line trying to diagnose it. If after replacing the pump the pressure is in a normal range then the pump was the issue and it was an easy fix...I can only hope that is the case.

If pressure is still low, how would I test the suction and discharge pressures? Is there a way you insert a T with a gauge onto either of those lines?

 

Sounds like a plan.

Testing the suction line you need to tee in a vacuum gauge at the pump suction. I have the specs for it somewhere.