Rich;
"Put a mechanical gauge in place of psi sensor".
I'm seeing that Ric put the gauge in place of the sender, and not in conjuction with it. Was showing the same 1psi result as what his Dynon was showing. SURE---having the gauge plumbed with a tee just before the sender would allow you to read BOTH the mechanical gauge and the Dynon from the same source to compare the readings. My FLAWED LOGIC says that if they are different with the gauge being higher and possibly more correct, then a faulty sender is a good candidate.
If they read the same, then check the hose and the source location.
If necessary, check it at the pump discharge port to verify the pressures.
IF the pressure is 'normal' at the pump, then there is some sort of anomaly between the pump, through the system to the gauge/sender location where you originally take the pressure readings. If the pump pressure is also low, then check the supply from the gascolator to the pump.
It is NOT beyond the realm of possibility that the supply hoses 'could' be partially collapsing under the suction of the pump, IF they are the rubber hose, and IF the pumps suction is sufficient enough to develop enough force to partially collapse the hose.
Ric didnt say whether or not his test was WITH the boost pump running or not. Since the plans call for the pump to be running all the time, I would assume his test was with the boost pump on. So--again FLAWED LOGIC, you would think that IF the boost pump were producing proper discharge pressure, then the fuel pressure supplied to the mechanical pump would be 2.5-5 psi ( or whatever it is). IF it is NOT ( as measured at the supply port of the mechanical pump) then obviously there is an issue with the supply system. Tank, tank vent, cabin lines, boost pump, flow transducer, gascolator, supply hose. Easiest test would be to open the fuel cap and create a large vent. Rerun the test and see if anything changes. IF everything operates normally, then FLAWED LOGIC would tell me to look at the vent system, and repair/update as necessary and retest.
IF the vent test yielded the same low pressure results, then there is something in the supply side.
IF the measured pressure was with the boost pump OFF----then recheck it with pump ON and see if the pressure rises. IF it doesnt, then check the boost pump pressure. Just because it may be running, doesnt mean it's producing the necessary pressure.
By systematically point by point testing and restesting you will find the problem. YES its time consuming but much less expensive than guessing and throwing a bunch of parts at this and seeing if that fixes the problem. Doing so may in fact 'fix' the problem for a while, but if you havent found the actual culprit, then it will occur again.
OH----I mentioned the rubber hose collapsing under suction. I dont KNOW that this is occurring. I DO KNOW that once in years past it occurred in an automotive application, where the rubber hose looked fine, until you took it off and looked through it. Guy was supposedly street racing and mixing octane booster and it literally eroded the liner to the point where the nylon braid was beginning to show. YEP===lots of debris in the filter. He thought it was bad fuel.
So---sorry for the long explanation, but troubleshooting this shouldnt be as difficult as it seems. YES, by all means, its a pain, and painstaking.
Tom