Fuel delivery (pump or filter?) problem - need advice on how to diagnose

[XH29N0G]

BSB67, I agree that the WOT test is important for knowing whether the pump is enough, but interpreted the idle test in the FSM as a way to determine if the pump was capable of delivering its specified pressure.  Also, the problem I ran into was not at WOT.

Also, The gauge I purchased is a Mr. Gasket 1561.  I noticed when I set it up that it did not read zero but instead read 2 psi.  I did not worry because the package the gauge came in said that it might not, but would as soon as it was put on the fuel line.  I took this at face value, but the baseline never returned to zero (instead settled to 2 PSI).  

Worried that the 4-5 PSI reading might be a false high reading, I just repeated the test with another gauge (a vacuum/pressure gauge) and the fuel pressure I measured at idle was 2-3 PSI - consistent with a miscalibration of the Mr. Gasket Gauge.  (4-5 with a 2 psi baseline comes out as 2-3).  

Both readings are less than 6-7.5 PSI, and I now suspect that this might indicate either the pump or the push rod is bad.  

I am going to continue with the plan check the push rod and to swap pumps.

CDR, I just checked the hoses and they look good.  Thanks for the suggestion.

[BSB67]

Irrespective of what the FSM says, test at idle is not a meaningful.  A pump with a worn push rod will generate pressure when there is no demand for the fuel, but once you drive down the street and the motor's fuel demand goes up, the pressure will fall off, the fuel level bowl will slowly go down, and the A/F will go up.   You simply cannot learn anything meaningful if you are not conducting the test when the problem is occurring.  The WOT test is just a simple and fast way to get to the correct answer about the pump without driving around until it dies on you.

Also, be sure the pressure gauge port is as close to the carb as possible.

Truly, if you really want to learn something, take it for a drive with the gauge in a readable position.

[XH29N0G]

Thank you.  This makes sense. 

I am trying to figure out how to put the gauge in a readable position and keep it close to the carburetor at the same time. 

Is it OK to snake a vacuum type hose out and tape the gauge to the windshield? Or is there another way?   

My guess is that the pressure can only be lower than the 3 PSI measured at idle, is the idea to look for it dropping lower and then not filling the bowls?

[BSB67]

pic - 1000 words

[XH29N0G]

Another pic.  I think I found my problem.  It will be a week before I have it back together (need a tap to clean some threads).  Thanks for all of the feedback and advice.  It helps a lot - especially for those of us who do not do this all the time and are always on a learning curve.  I will see what the pressure is with the other pump and new pushrod.  

Are there any tips/advice on reassembly?

[A383Wing]

use some wheel bearing grease to hold the rod up in the hole when putting it all back together, also turn the engine over so the rod is at it's highest point in the block to ease installing the pump

[XH29N0G]

Thanks.